EXHIBIT 23.1 CONSENT OF INDEPENDENT AUDITORS We consent to the incorporation by reference in the Registration Statements (Form S-8 No. 333-57046, 2-85628, 33-15102, 33-87662, 33-87664, 333-17513, and 333-106385; Form S-3 No. 333-63777, 333-63773, 333-65125, 333-40716, 333-66350, 333-71086, and 333-103965) of Peregrine Pharmaceuticals, Inc. of our report dated June 20, 2003 (except for Notes 8, 10, and 17, as to which the date is July 2, 2003) with respect to the consolidated financial statements and schedule of Peregrine Pharmaceuticals, Inc. included in the Annual Report (Form 10-K) for the year ended April 30, 2003. /s/ ERNST & YOUNG LLP Orange County, California July 25, 2003