- John Phillip Law
- Diabolik
- Marisa Mell
- Eva Kant
- Michel Piccoli
- Inspector Ginko
- Adolfo Celi
- Ralph Valmont
- Claudio Gora
- Police Chief
- Mario Donen
- Sergeant Danek
- Renzo Palmer
- Mr. Hammond
- Caterina Boratto
- Lady Clark
- Lucia Modugno
- Prostitute
- Annie Gorassini
- Rose
- Carlo Croccolo
- Lorry Driver
- Lidia Biondi
- Policewoman
- Andrea Bosic
- Bank Manager
- Federico Boido
- Joe
- Tiberio Mitri
- Valmont's Henchman #1
- Isarco Ravaioli
- Valmont's Henchman #2
- Giorgio Sciolette
- Dr. Ferrar
- Terry-Thomas
- Minister of the Interior / Minister of Finance (as Terry Thomas)
- Bruno Alias
- Party Guest
- Ennio Antonelli
- Syndicate Member
- Fausto Beffa
- Soldier on Train
- Franco Bellucci
- Fake Diplomat
- Regina Elena Bisio
- Old Woman at Morgue
- Giuseppe Cardone
- Syndicate Member
- Lella Cattaneo
- Party Guest
- Massimo Ciprari
- Fake Diplomat
- Franz Colangeli
- Party Guest
- Bruno Degni
- Man at Press Conference
- Giulio Donnini
- Dr. Vernier
- Raniero Dorascenzi
- Party Guest
- Sandro Dori
- Stud
- Giuseppe Fazio
- Tony
- Giorgio Gennari
- Rudy - Valmont's Henchman
- Renzo Granelli
- Party Guest
- Guidarino Guidi
- Frank - Syndicate Member
- Wolfgang Hillinger
- Valmont's Henchman
- Mario Ingrassia
- Party Guest
- Augusto Innocenzi
- Party Guest
- Edward Febo Kelleng
- Sir Harold Clark
- Silvio Klein
- Journalist at Press Conference
- Enzo Mondino
- Journalist at Press Conference / Party Guest (uncredited)
- Francesco Mulè
- Crematoria Operator
- Vezio Natili
- Party Guest
- Chuck Painter
- Newscaster
- Orlando Pallamari
- Mr. Hammond's Secretary
- Angela Palmieri
- Dr. Vernier's Nurse
- Vito Passeri
- Man Watching TV
- Anita Peccioli
- Junkie
- Attilio Pelegatti
- Man Asking for Ginko
- Filippo Perego
- Party Guest
- Domenico Ravenna
- Party Guest
- Manlio Salvatori
- Party Guest
- Oscar Sciamanna
- Journalist
- Walter Williams
- Man in Charge of Gold
- Milena Zampana
- Party Guest