Exhibit 5.1

February 15, 2005

Re: Registration Statement on Form S-8

Ladies and Gentlemen:

I am Executive Vice President, General Counsel and Secretary of CACI International Inc (the “Company).

This opinion is being furnished in connection with the registration on Form S-8 (the “Registration Statement”) under the Securities Act of 1933, as amended of 1,500,000 shares of the Company’s Class A Common Stock (the “Common Stock”) which may be offered and sold under the 1996 Stock Incentive Plan (As Amended September 22, 2004) (the “Plan”).

I am of the opinion that if, as and when the shares of Common Stock are issued and sold and consideration therefore is received pursuant to the provisions of the Plan and in accordance with the Registration Statement, such shares will be duly authorized, legally issued, fully paid and non-assessable.

I consent to the filing of this opinion letter as Exhibit 5.1 to the Registration Statement.

Very truly yours,

/s/ Jeffrey P. Elefante

Jeffrey P. Elefante

Executive Vice President

General Counsel and Secretary