Exhibit 99.1

For Immediate Release

Isabella Bank Corporation

401 North Main Street

Mt. Pleasant, MI 48858-1649

FOR MORE INFORMATION CONTACT:

Lori Peterson, Director of Marketing

Phone: 989-779-6333 Fax: 989-775-5501

Isabella Bank Corporation Announces Fourth Quarter and 2023 Earnings

Continued growth in loans, Isabella Wealth; outpaced by continued interest rate pressure

Mt. Pleasant, Michigan, February 16, 2024 — Isabella Bank Corporation (the “Corporation”) (OTCQX: ISBA) reported fourth quarter and year-end 2023 earnings, demonstrating resilience during a year buffeted by rising interest rates on deposit accounts. Net income for the fourth quarter was $3.8 million and $18.2 million for the year ended December 31, 2023. Earnings per common share were $0.51 in the fourth quarter and $2.42 for the year.

Among the 2023 highlights:

•Gross loans increased more than $85 million, or 7%.

•Isabella Wealth assets grew 25% to $641 million, leading to an increase in wealth management fees of $552,000, or 18%, over 2022.

•Interest income increased $13.8 million, or 21%, over 2022, offset by an increase in interest expense of $16.4 million.

•Shareholders earned a cash dividend of $1.12 per share in 2023, with an annualized dividend yield of 5.21%.

“Our 2023 financial results demonstrate Isabella Bank’s ability to come out of a tough year still delivering strong results for shareholders,” said Jerome E. Schwind, President and Chief Executive Officer. "Our liquidity and capital ratios remain strong and we delivered results against our strategic plan based on our strength in the marketplace.

"We continued to grow our footprint — including adding our eighth mid-Michigan county — and customers continued to turn to Isabella Bank, driving our growth in loans and our wealth management business,” he added.

Operating Results

Net income: Net income for the fourth quarter of 2023 was $3.8 million, a decrease of $2.5 million compared to the same period in 2022. For the year ended December 31, 2023, net income was $18.2 million, compared to $22.2 million in 2022. The declines were driven by a rise in interest expense resulting largely from increased interest rates on deposit accounts.

Net interest income, fourth quarter 2023: Net interest income for the fourth quarter 2023 declined $2.7 million, or 16%, compared to the fourth quarter of 2022. Interest income increased $3.1 million, or 17.5%, driven by core loan growth, while continued interest rate pressure was the primary cause of a $5.8 million increase in interest expense over the same period in 2022.

Net interest income, year-end 2023: Net interest income for the year ended December 31, 2023 decreased $2.5 million, or 4.2%, compared to 2022. Rising interest rates and growth in core loans led to a $13.8 million, or 21%, increase in gross interest income during 2023, compared to 2022. At the same time, rising interest rates on deposits and an increase in borrowings led to a $16.4 million increase in interest expense for 2023, compared to 2022.

Noninterest income and expenses, fourth quarter 2023: Noninterest income increased $244,000 compared to the fourth quarter of 2022, primarily driven by wealth management fees and ATM and debit card income. Noninterest expenses for the quarter were essentially unchanged in comparison to the fourth quarter of 2022.

Noninterest income and expenses, year-end 2023: Noninterest income for the year ended December 31, 2023 increased $161,000 compared to 2022. The increase was driven by wealth management fees and ATM and debit card fee income, offset by a decrease in mortgage servicing rights and gain on sale of loans, as residential mortgages sold to the secondary market declined. Noninterest expense increased $2.5 million compared to 2022, primarily the result of increased compensation, equipment expense, other losses, and FDIC insurance premiums.

Net yield on interest earning assets: The Corporation’s fully taxable equivalent net yield on interest earning assets was 2.85% and 3.05% for the fourth quarter and year ended December 31, 2023, respectively, compared to 3.43% and 3.18% for the same periods in 2022. To maintain a competitive edge in the rising interest rate environment, rates on several deposit products began to increase in the fourth quarter of 2022 and continued throughout 2023. Over the last year, the level of borrowings increased to fund loan growth. These factors have negatively impacted the net yield on interest earning assets slowing its rate of growth.

Balance Sheet

Assets: Total assets were $2.06 billion and assets under management were $2.95 billion as of December 31, 2023. Managed assets included loans sold and serviced of $249 million as well as $641 million in investment and trust assets managed by our wealth business.

Loans: Loans outstanding as of December 31, 2023 totaled $1.35 billion, growing $85.3 million since December 31, 2022. Credit quality remained strong, as evidenced by total past due and nonaccrual loans which were 0.37% of gross loans as of December 31, 2023.

Deposits: Deposits were $1.72 billion as of December 31, 2023, declining $20.6 million, or 1.2%, since December 31, 2022. A decline in demand deposits was driven by contraction in money supply as the Federal Reserve Bank pulled money out of the banking system.

Capital: The Bank continues to be considered a “well-capitalized” institution, as its capital ratios exceeded the minimum designated requirements. As of December 31, 2023, the Bank’s Tier 1 Leverage Ratio was 8.71%, Tier 1 Capital Ratio was 12.48% and Total Capital Ratio was 13.42%, compared to minimum requirements to be considered well capitalized of 5.0%, 8.0% and 10.0%, respectively.

Dividend: The Corporation paid a $0.28 per common share cash dividend for the fourth quarter of 2023. Total cash dividends paid for the year ended December 31, 2023 totaled $1.12, a 2.75% increase over dividends paid in 2022. Based on the Corporation’s closing stock price of $21.50 as of December 29, 2023, the annualized cash dividend yield was 5.21%.

About the Corporation

Isabella Bank Corporation (OTCQX: ISBA) is the parent holding company of Isabella Bank, a state-chartered community bank headquartered in Mt. Pleasant, Michigan. Isabella Bank was established in 1903 and has been committed to serving its customers' and communities' local banking needs for over 120 years. The Bank offers personal and commercial lending and deposit products, as well as investment, trust, and estate planning services. The Bank has locations throughout eight Mid-Michigan counties: Bay, Clare, Gratiot, Isabella, Mecosta, Midland, Montcalm, and Saginaw.

For more information about Isabella Bank Corporation, visit the Investor Relations link at www.isabellabank.com. Isabella Bank Corporation common stock is quoted on the OTCQX tier of the OTC Markets Group, Inc.’s electronic quotation system (www.otcmarkets.com) under the symbol “ISBA.” The Corporation’s investor relations firm is Stonegate Capital Partners, Inc. (www.stonegateinc.com).

Forward-Looking Statements

This press release includes forward-looking statements. To the extent that the foregoing information refers to matters that may occur in the future, please be aware that such forward-looking statements may differ materially from the actual results. Additional information concerning some of the factors that could cause materially different results is included in the sections titled “Risk Factors” and “Forward Looking Statements” set forth in Isabella Bank Corporation’s filings with the Securities and Exchange Commission, which are available from the Securities and Exchange Commission’s Public Reference facilities and from its website at www.sec.gov.

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED)

(Dollars in thousands)

			December 31 2023						December 31 2022
ASSETS
Cash and cash equivalents
Cash and demand deposits due from banks			$	25,628					$	27,420
Fed Funds sold and interest bearing balances due from banks			8,044						11,504
Total cash and cash equivalents			33,672						38,924
Available-for-sale securities, at fair value			528,148						580,481
Mortgage loans available-for-sale			—						379
Loans			1,349,463						1,264,173
Less allowance for credit losses			13,108						9,850
Net loans			1,336,355						1,254,323
Premises and equipment			27,639						25,553
Corporate owned life insurance policies			33,892						32,988
Equity securities without readily determinable fair values			15,848						15,746
Goodwill and other intangible assets			48,284						48,287
Accrued interest receivable and other assets			35,130						33,586
TOTAL ASSETS			$	2,058,968					$	2,030,267
LIABILITIES AND SHAREHOLDERS’ EQUITY
Deposits
Noninterest bearing			$	428,505					$	494,346
Interest bearing demand deposits			320,737						372,155
Certificates of deposit under $250 and other savings			857,768						810,642
Certificates of deposit over $250			116,685						67,132
Total deposits			1,723,695						1,744,275
Borrowed funds
Federal funds purchased and repurchase agreements			46,801						57,771
Federal Home Loan Bank advances			40,000						—
Subordinated debt, net of unamortized issuance costs			29,335						29,245
Total borrowed funds			116,136						87,016
Accrued interest payable and other liabilities			16,735						12,766
Total liabilities			1,856,566						1,844,057
Shareholders’ equity
Common stock — no par value 15,000,000 shares authorized; issued and outstanding 7,485,889 shares (including 150,581 shares held in the Rabbi Trust) in 2023 and 7,559,421 shares (including 154,879 shares held in the Rabbi Trust) in 2022			127,323						128,651
Shares to be issued for deferred compensation obligations			3,693						5,005
Retained earnings			97,282						89,748
Accumulated other comprehensive income (loss)			(25,896)						(37,194)
Total shareholders’ equity			202,402						186,210
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY			$	2,058,968					$	2,030,267

CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)

(Dollars in thousands except per share amounts)

			Three Months Ended   December 31												Year Ended  December 31
			2023						2022						2023						2022
Interest income
Loans, including fees			$	17,580					$	14,163					$	65,670					$	53,283
Available-for-sale securities
Taxable			2,303						2,512						9,514						8,363
Nontaxable			623						718						2,642						2,808
Federal funds sold and other			550						522						1,805						1,344
Total interest income			21,056						17,915						79,631						65,798
Interest expense
Deposits			6,399						1,323						18,352						4,021
Borrowings
Federal funds purchased and repurchase agreements			357						53						961						79
Federal Home Loan Bank advances			422						—						1,309						152
Subordinated debt, net of unamortized issuance costs			266						267						1,065						1,065
Total interest expense			7,444						1,643						21,687						5,317
Net interest income			13,612						16,272						57,944						60,481
Provision for credit losses			684						(57)						629						483
Net interest income after provision for credit losses			12,928						16,329						57,315						59,998
Noninterest income
Service charges and fees			2,212						2,115						8,297						8,730
Wealth management fees			932						788						3,557						3,005
Earnings on corporate owned life insurance policies			239						229						920						884
Net gain on sale of mortgage loans			85						63						317						631
Other			48						77						736						416
Total noninterest income			3,516						3,272						13,827						13,666
Noninterest expenses
Compensation and benefits			6,116						6,407						25,905						24,887
Furniture and equipment			1,697						1,624						6,519						6,006
Occupancy			857						878						3,778						3,691
Other			3,245						3,013						13,108						12,236
Total noninterest expenses			11,915						11,922						49,310						46,820
Income before federal income tax expense			4,529						7,679						21,832						26,844
Federal income tax expense			726						1,357						3,665						4,606
NET INCOME			$	3,803					$	6,322					$	18,167					$	22,238
Earnings per common share
Basic			$	0.51					$	0.84					$	2.42					$	2.95
Diluted			$	0.51					$	0.83					$	2.40					$	2.91
Cash dividends per common share			$	0.28					$	0.28					$	1.12					$	1.09

AVERAGE BALANCES, INTEREST RATE, AND NET INTEREST INCOME (UNAUDITED)

(Dollars in thousands)

The following schedules present the daily average amount outstanding for each major category of interest earning assets, non-earning assets, interest bearing liabilities, and noninterest bearing liabilities. These schedules also present an analysis of interest income and interest expense for the periods indicated. All interest income is reported on a fully taxable equivalent (FTE) basis using a federal income tax rate of 21%. Loans in nonaccrual status, for the purpose of the following computations, are included in the average loan balances. Federal Reserve Bank (FRB) and Federal Home Loan Bank (FHLB) restricted equity holdings are included in other interest earning assets.

			Three Months Ended
			December 31, 2023																		December 31, 2022
			Average Balance						Tax Equivalent Interest						Average Yield / Rate						Average Balance						Tax Equivalent Interest						Average Yield / Rate
INTEREST EARNING ASSETS
Loans (1)			$	1,340,271					$	17,580					5.25		%				$	1,244,972					$	14,163					4.55		%
Taxable investment securities			473,660						2,274						1.92		%				520,139						2,499						1.92		%
Nontaxable investment securities			90,408						899						3.98		%				107,508						999						3.72		%
Fed funds sold			13						—						5.76		%				14						—						4.00		%
Other			39,585						549						5.55		%				56,142						522						3.72		%
Total earning assets			1,943,937						21,302						4.38		%				1,928,775						18,183						3.77		%
NONEARNING ASSETS
Allowance for credit losses			(12,780)																		(9,792)
Cash and demand deposits due from banks			23,244																		24,312
Premises and equipment			27,444																		25,382
Accrued income and other assets			71,592																		63,553
Total assets			$	2,053,437																	$	2,032,230
INTEREST BEARING LIABILITIES
Interest bearing demand deposits			$	317,996					$	504					0.63		%				$	358,809					$	104					0.12		%
Savings deposits			634,539						2,819						1.78		%				635,771						535						0.34		%
Time deposits			338,852						3,076						3.63		%				254,604						684						1.07		%
Federal funds purchased and repurchase agreements			50,049						357						2.85		%				55,478						53						0.38		%
Federal Home Loan Bank advances			29,674						422						5.69		%				—						—						—		%
Subordinated debt, net of unamortized issuance costs			29,320						266						3.63		%				29,233						267						3.65		%
Total interest bearing liabilities			1,400,430						7,444						2.13		%				1,333,895						1,643						0.49		%
NONINTEREST BEARING LIABILITIES
Demand deposits			446,747																		504,791
Other			17,302																		13,103
Shareholders’ equity			188,958																		180,441
Total liabilities and shareholders’ equity			$	2,053,437																	$	2,032,230
Net interest income (FTE)									$	13,858																	$	16,540
Net yield on interest earning assets (FTE)															2.85		%																3.43		%

(1) Includes loans and mortgage loans available-for-sale

			Year Ended
			December 31, 2023																		December 31, 2022
			Average Balance						Tax Equivalent Interest						Average Yield / Rate						Average Balance						Tax Equivalent Interest						Average Yield / Rate
INTEREST EARNING ASSETS
Loans (1)			$	1,308,891					$	65,670					5.02		%				$	1,249,634					$	53,283					4.26		%
Taxable investment securities			485,718						9,399						1.94		%				477,159						8,294						1.74		%
Nontaxable investment securities			96,845						3,780						3.90		%				107,158						3,933						3.67		%
Fed funds sold			12						1						5.04		%				10						—						2.42		%
Other			41,965						1,804						4.30		%				99,301						1,344						1.35		%
Total earning assets			1,933,431						80,654						4.17		%				1,933,262						66,854						3.46		%
NONEARNING ASSETS
Allowance for credit losses			(12,784)																		(9,477)
Cash and demand deposits due from banks			24,592																		24,708
Premises and equipment			26,589																		24,648
Accrued income and other assets			74,319																		81,823
Total assets			$	2,046,147																	$	2,054,964
INTEREST BEARING LIABILITIES
Interest bearing demand deposits			$	346,875					$	1,086					0.31		%				$	374,623					$	274					0.07		%
Savings deposits			626,027						8,290						1.32		%				630,574						1,135						0.18		%
Time deposits			308,699						8,976						2.91		%				270,296						2,612						0.97		%
Federal funds purchased and repurchase agreements			43,061						961						2.23		%				49,974						79						0.16		%
Federal Home Loan Bank advances			23,699						1,309						5.52		%				7,863						152						1.93		%
Subordinated debt, net of unamortized issuance costs			29,287						1,065						3.64		%				29,200						1,065						3.65		%
Total interest bearing liabilities			1,377,648						21,687						1.57		%				1,362,530						5,317						0.39		%
NONINTEREST BEARING LIABILITIES
Demand deposits			461,689																		482,781
Other			16,043																		14,695
Shareholders’ equity			190,767																		194,958
Total liabilities and shareholders’ equity			$	2,046,147																	$	2,054,964
Net interest income (FTE)									$	58,967																	$	61,537
Net yield on interest earning assets (FTE)															3.05		%																3.18		%

(1) Includes loans and mortgage loans available-for-sale

SELECTED FINANCIAL DATA (UNAUDITED)

(Dollars in thousands except per share amounts)

			Year Ended
			December 31 2023						December 31 2022						December 31 2021
PER SHARE
Basic earnings			$	2.42					$	2.95					$	2.48
Diluted earnings			$	2.40					$	2.91					$	2.45
Dividends			$	1.12					$	1.09					$	1.08
Tangible book value			$	20.59					$	18.25					$	21.61
Quoted market value
High			$	26.00					$	26.25					$	29.00
Low			$	19.13					$	21.00					$	19.45
Close (1)			$	21.50					$	23.50					$	25.50
Common shares outstanding (1)			7,485,889						7,559,421						7,532,641
Average number of common shares outstanding			7,511,591						7,549,878						7,853,398
Average number of diluted common shares outstanding			7,575,492						7,647,612						7,965,961
PERFORMANCE RATIOS
Return on average total assets			0.89		%				1.08		%				0.96		%
Return on average shareholders' equity			9.52		%				11.41		%				8.83		%
Return on average tangible shareholders' equity			12.75		%				15.17		%				11.31		%
Net interest margin yield (FTE)			3.05		%				3.18		%				2.87		%
ASSETS UNDER MANAGEMENT (1)
Loans sold with servicing retained			$	248,756					$	264,206					$	278,844
Assets managed by Isabella Wealth			$	641,027					$	513,918					$	516,243
Total assets under management			$	2,948,751					$	2,808,391					$	2,827,245
ASSET QUALITY (1)
Nonaccrual loans			$	982					$	457					$	1,245
Foreclosed assets			$	406					$	439					$	211
Net loan charge-offs (recoveries)			$	115					$	(264)					$	123
Nonperforming loans to gross loans			0.08		%				0.04		%				0.10		%
Nonperforming assets to total assets			0.07		%				0.05		%				0.08		%
Allowance for credit losses to gross loans			0.97		%				0.78		%				0.70		%
CAPITAL RATIOS (1)
Shareholders' equity to assets			9.83		%				9.17		%				10.39		%
Tier 1 leverage			8.76		%				8.61		%				7.97		%
Common equity tier 1 capital			12.54		%				12.91		%				12.07		%
Tier 1 risk-based capital			12.54		%				12.91		%				12.07		%
Total risk-based capital			15.52		%				15.79		%				14.94		%

(1) At end of period

SUPPLEMENTAL BALANCE SHEET DATA (UNAUDITED)

(Dollars in thousands)

			December 31 2023						September 30 2023						June 30 2023						March 31 2023						December 31 2022
Commercial and industrial			$	209,738					$	195,814					$	194,914					$	189,185					$	178,428
Commercial real estate			564,244						566,639						564,254						566,410						566,012
Advances to mortgage brokers			18,541						24,807						39,099						—						—
Agricultural			99,994						99,233						96,689						94,760						104,985
Residential real estate			356,418						348,196						343,474						336,186						336,694
Consumer			100,528						99,985						95,972						84,110						78,054
Gross loans			$	1,349,463					$	1,334,674					$	1,334,402					$	1,270,651					$	1,264,173

			December 31 2023						September 30 2023						June 30 2023						March 31 2023						December 31 2022
Noninterest bearing demand deposits			$	428,505					$	445,043					$	458,845					$	478,829					$	494,346
Interest bearing demand deposits			320,737						363,558						335,922						383,602						372,155
Savings deposits			628,079						628,795						606,644						662,495						625,734
Certificates of deposit			346,125						331,829						313,288						288,103						251,541
Internet certificates of deposit			249						249						249						499						499
Total deposits			$	1,723,695					$	1,769,474					$	1,714,948					$	1,813,528					$	1,744,275

			December 31 2023						September 30 2023						June 30 2023						March 31 2023						December 31 2022
U.S. Treasury			$	214,801					$	209,182					$	209,353					$	212,086					$	208,701
States and political subdivisions			92,876						89,773						95,242						108,719						117,512
Auction rate money market preferred			2,931						2,570						2,637						2,716						2,342
Mortgage-backed securities			32,815						32,923						35,532						37,797						39,070
Collateralized mortgage obligations			177,775						175,630						180,996						200,252						205,728
Corporate			6,950						6,819						6,737						7,080						7,128
Available-for-sale securities, at fair value			$	528,148					$	516,897					$	530,497					$	568,650					$	580,481

			December 31 2023						September 30 2023						June 30 2023						March 31 2023						December 31 2022
Securities sold under agreements to repurchase without stated maturity dates			$	46,801					$	52,330					$	37,102					$	31,995					$	57,771
Federal Home Loan Bank advances			40,000						65,000						55,000						—						—
Subordinated debt, net of unamortized issuance costs			29,335						29,312						29,290						29,267						29,245
Total borrowed funds			$	116,136					$	146,642					$	121,392					$	61,262					$	87,016

SUPPLEMENTAL STATEMENTS OF INCOME DATA (UNAUDITED)

(Dollars in thousands)

			Three Months Ended   December 31												Year Ended  December 31
			2023						2022						2023						2022
Service charges and fees
ATM and debit card fees			$	1,397					$	1,267					$	5,051					$	4,774
Service charges and fees on deposit accounts			616						653						2,413						2,566
Freddie Mac servicing fee			155						163						630						669
Net mortgage servicing rights income (loss)			(40)						(42)						(137)						435
Other fees for customer services			84						74						340						286
Total service charges and fees			2,212						2,115						8,297						8,730
Wealth management fees			932						788						3,557						3,005
Earnings on corporate owned life insurance policies			239						229						920						884
Net gain on sale of mortgage loans			85						63						317						631
Other			48						77						736						416
Total noninterest income			$	3,516					$	3,272					$	13,827					$	13,666

			Three Months Ended   December 31												Year Ended  December 31
			2023						2022						2023						2022
Compensation and benefits			$	6,116					$	6,407					$	25,905					$	24,887
Furniture and equipment			1,697						1,624						6,519						6,006
Occupancy			857						878						3,778						3,691
Other
Audit, consulting, and legal fees			576						609						2,340						2,358
ATM and debit card fees			487						424						1,767						1,909
Marketing costs			276						244						1,159						1,056
Memberships and subscriptions			313						222						1,042						876
Loan underwriting fees			290						364						927						1,004
FDIC insurance premiums			233						143						922						537
Donations and community relations			223						258						915						923
Other losses			101						137						871						546
Director fees			183						192						764						790
All other			563						420						2,401						2,237
Total other noninterest expenses			3,245						3,013						13,108						12,236
Total noninterest expenses			$	11,915					$	11,922					$	49,310					$	46,820