Exhibit 5.1

[Letterhead of Wilson Sonsini Goodrich & Rosati, P.C.]

December 14, 2011

Integrated Silicon Solution, Inc.

1940 Zanker Road

San Jose, CA 95112

Re: Registration Statement on Form S-8

Ladies and Gentlemen:

We have examined the Registration Statement on Form S-8 to be filed by you with the Securities and Exchange Commission on or about the date hereof (the “Registration Statement”) in connection with the registration under the Securities Act of 1933, as amended (the “Act”), of an additional 2,000,000 shares (the “Shares”) of your Common Stock issuable under your 2007 Incentive Compensation Plan (the “Plan”). As your counsel, we have examined the proceedings taken and are familiar with the proceedings proposed to be taken by you in connection with the issuance and sale of the Shares pursuant to the Plan.

It is our opinion that, when issued and sold in the manner described in the Plan and pursuant to the agreements which accompany each grant under the Plan, the Shares will be legally and validly issued, fully-paid and non-assessable.

We consent to the use of this opinion as an exhibit to the Registration Statement, and further consent to the use of our name wherever appearing in the Registration Statement and any amendments thereto.

Very truly yours,

WILSON SONSINI GOODRICH & ROSATI

Professional Corporation

/s/ Wilson Sonsini Goodrich & Rosati, P.C.