Robert Lamoureux

Arsène Lupin / Lieutenant André Laroche

Robert Dalban

Inspector Béchoux of the Judicial Police

Alida Valli

Aurélia Valéano

Jacques Dufilho

Albert, manservant

Yves Robert

La Ballu

Roger Dumas

Isidore Bautrelet aka 'Véritaz'

Hubert de Lapparent

French Consul in Florence

Jean Bellanger

Sleeping car employee

Michel Etcheverry

Van Nelden, collector

Jean Galland

General

Gisèle Grandpré

Madame du Bois-Lambert

Paul Müller

Attaché of the French consulate in Florence

Ginette Pigeon

Agnès, nurse

Michel Vocoret

Gérard Darrieu

Sidekick

Gabriel Gobin

SNCF employee (uncredited)

René Hell

Prison guard (uncredited)

René Lefèvre-Bel

(uncredited)

Judith Magre

(uncredited)

Paul Préboist

Drunkard of Enghien (uncredited)

Robert Rollis

Traveler on the train (uncredited)

Paul Villé

Secretary of the archives (uncredited)