Holt of the Secret Service

Jack Holt

Jack Holt / Nick Farrell

Evelyn Brent

Kay Drew

John Ward

'Lucky' Arnold

Ted Adams

Quist

Joe McGuinn

'Crimp' Evans [Chs. 1, 4-15]

Tris Coffin

Ed Valdin [Chs. 1-10]

Stanley Blystone

Garrity [Chs. 11-15]

George Chesebro

Rankin [Chs. 11-15]

Stanley Price

Dent [Chs. 11-15]

C. Montague Shaw

Chief John W. Malloy (as Montague Shaw)

Edward Hearn

Agent Jim Layton

Jack Cheatham

Agent Frank [Chs. 3-5, 8-9, 15]

Ray Parsons

John Severn - Engraver [Chs. 1-4]