Spencer Tracy as Henry M. Stanley

Nancy Kelly as Eve Kingsley

Richard Greene as Gareth Tyce

Walter Brennan as Jeff Slocum

Charles Coburn as Lord Tyce

Cedric Hardwicke as Dr. David Livingstone

Henry Hull as James Gordon Bennett, Jr.

Henry Travers as John Kingsley

Miles Mander as Sir John Gresham

David Torrence as Mr. Cranston

Holmes Herbert as Frederick Holcomb

C. Montague Shaw as Sir Oliver French

Brandon Hurst as Sir Henry Forrester

Hassan Said as Hassan

Paul Harvey as Colonel Grimes

Russell Hicks as Commissioner

Frank Dae as Commissioner

Ernest Baskett as Zucco

William E. 'Red' Blair as Sergeant

Everett Brown as Bongo

Bobby Burns as Geographical Society Delegate

Jack Clisby as Mombay

Tom Coleman as Corporal

Joseph Crehan as Morehead

Vernon Dent as Newspaperman in Office

Clarence Derwent as Sir Francis Vane

William R. Dunn as Chuma

Harry Harvey as Newspaperman at Water Barrel

Frank Jaquet as Senator

Darby Jones as Chewing Native

Eric Lonsdale as Reporter at Dock

Anthony Marsh as Messenger

James McNamara as Committeeman

Robert Middlemass as Carmichael

Clive Morgan as Reporter at Dock

Frank Orth as Newspaperman with Pills

Imboden Parrish as Reporter at Dock

Speirs Ruskell as Messenger

Emmett Smith as Susi

Dick Stanley as Lieutenant

Harry Strang as Captain

F. Philip Sylvestre as Messenger

Emmett Vogan as Albert

Billy Watson as Billy Watson

William B. Williams as Mace