- Al Pacino
- Serpico
- John Randolph
- Sidney Green
- Jack Kehoe
- Tom Keough
- Biff McGuire
- Captain McClain
- Barbara Eda-Young
- Laurie
- Cornelia Sharpe
- Leslie
- Tony Roberts
- Bob Blair
- John Medici
- Pasquale
- Allan Rich
- D.A. Tauber
- Norman Ornellas
- Rubello
- Edward Grover
- Lombardo
- Albert Henderson
- Peluce
- Hank Garrett
- Malone
- Damien Leake
- Joey
- Joseph Bova
- Potts
- Gene Gross
- Captain Tolkin
- John Stewart
- Waterman
- Woodie King Jr.
- Larry
- James Tolkan
- Steiger
- Ed Crowley
- Barto
- Bernard Barrow
- Palmer
- Sal Carollo
- Mr. Serpico
- Mildred Clinton
- Mrs. Serpico
- Nathan George
- Smith
- Gus Fleming
- Dr. Metz
- Richard Foronjy
- Corsaro
- Alan North
- Brown
- Lewis J. Stadlen
- Berman
- John McQuade
- Kellogg
- Ted Beniades
- Al Sarno
- John Lehne
- Gilbert
- M. Emmet Walsh
- Gallagher
- George Ede
- Daley
- Charles White
- Delaney
- F. Murray Abraham
- Detective Partner
- Wade Barnes
- Man
- P.J. Benjamin
- Man
- Don Billett
- Detective Threatening Serpico
- Val Bisoglio
- Weapons Storage Officer
- Raleigh Bond
- (uncredited)
- Sully Boyar
- Principal
- John Brandon
- Police Lieutenant
- James Bulleit
- Det. Styles
- Roy Cheverie
- Cop
- Sam Coppola
- Cop
- Marjorie Eliot
- Rape Victim
- René Enríquez
- Cervantes Teacher
- Conard Fowkes
- Cop - Narcotics Raid
- Ron Gilbert
- Cop
- Frank Gio
- Police Lieutenant
- Trent Gough
- Cop
- Paul E. Guskin
- Police Academy Classmate
- Nick Hardin
- Television Cameraman
- Judd Hirsch
- Cop
- Bianca Hunter
- (uncredited)
- Richard Kuss
- Detective
- Ben Lautman
- Bar Patron
- Tony Lo Bianco
- Cop
- George Loros
- Det. Glover
- Kenneth McMillan
- Charlie
- Judd Omen
- Doctor
- Stephen Pearlman
- Desk Sergeant
- Tim Pelt
- Black Hood
- William Pelt
- Black Hood
- Jay Rasumny
- Television Cameraman
- Franklin Scott
- Black Prisoner
- Jill Senter
- Hippy
- Tom Signorelli
- Bookmaker
- Ben Slack
- Detective Sitting at Desk
- Jaime Sánchez
- Cop
- Palombizio Anthony V.
- Street Vendor
- Steve Vignari
- Gambling Ring Hood
- Tracey Walter
- Street Urchin
- Charles Weldon
- Police Sergeant
- Mary Louise Weller
- Sally - Girl at Party
