1
                                                                     EXHIBIT 5.1

April 6, 2000

Saba Software, Inc.
2400 Bridge Parkway
Redwood Shores, CA  94065

Ladies and Gentlemen:

        We have examined the Registration Statement on Form S-8 to be filed by
Saba Software, Inc., a Delaware corporation (the "Company"), with the Securities
and Exchange Commission on April 6, 2000 (the "Registration Statement"),
relating to the registration under the Securities Act of 1933, as amended, of
2,000,000 shares of the Company's Common Stock, $0.001 par value (the "Shares").
The Shares are reserved for issuance pursuant to the Company's 2000 Employee
Stock Purchase Plan. As counsel to the Company, we have examined the proceedings
taken by the Company in connection with the registration of the Shares.

        It is our opinion that the Shares, when issued and sold in the manner
described in the Registration Statement and the related Prospectus, will be
legally and validly issued, fully paid and nonassessable.

        We consent to the use of this opinion as an exhibit to the Registration
Statement and further consent to all references to us in the Registration
Statement and any amendments thereto.

                                   Very truly yours,

                                   /s/ Morrison & Foerster LLP