
<PAGE>   1
                                                                   EXHIBIT 5.1



                    [FULBRIGHT & JAWORSKI L.L.P. LETTERHEAD]



May 31, 1995

Stewart Information Services Corporation
1980 Post Oak Boulevard
Houston, Texas  77056

Gentlemen:

             We have acted as counsel for Stewart Information Services
Corporation, a Delaware corporation (the "Company"), in connection with the
registration under the Securities Act of 1933 of 100,000 shares of the Company's
common stock, $1.00 par value (the "Shares"), to be offered upon the terms and
subject to the conditions set forth in the Company's 1995 Stock Option Plan (the
"Plan").

             In connection therewith, we have examined originals or copies,
certified or otherwise identified to our satisfaction, of the Certificate of
Incorporation of the Company, as amended, the By-Laws of the Company, as
amended, the Plan, records of relevant corporate proceedings with respect to the
offering of the Shares and such other documents and instruments as we have
deemed necessary or appropriate for the expression of the opinions contained
herein. We have also reviewed the Company's Registration Statement on Form S-8
to be filed with the Securities and Exchange Commission with respect to the
Shares (the "Registration Statement").

             We have assumed the authenticity and completeness of all records,
certificates and other instruments submitted to us as originals, the conformity
to original documents of all records, certificates and other instruments
submitted to us as copies, the authenticity and completeness of the originals of
those records, certificates and other instruments submitted to us as copies and
the correctness of all statements of fact contained in all records, certificates
and other instruments that we have examined.

             Based on the foregoing and having regard for such legal
considerations as we have deemed relevant, we are of the opinion that the Shares
have been duly authorized and, when issued in accordance with the terms of the
Plan, will be validly issued, fully paid and non-assessable.

             The opinions expressed herein are limited exclusively to the
General Corporation Law of the State of Delaware.



<PAGE>   2

June 1, 1995
Page 2

             We hereby consent to the filing of this opinion as an exhibit to
the Registration Statement.

                                            Very truly yours,


                                            Fulbright & Jaworski L.L.P.

