William Boyd

as Hopalong Cassidy

Andy Clyde

as California Carlson

Rand Brooks

as Lucky Jenkins

Robert Emmett Keane

as Professor Dixon

Jane Randolph

as Jessie Dixon

Fred 'Snowflake' Toones

as Speed

Steve Barclay

as Bruce Landy

Harry Cording

as Duke

Earle Hodgins

as Sandler

Robert Bentley

as Barton

William 'Wee Willie' Davis

as Blackie

Forbes Murray

as Colonel Jed Landy

Glen Gallagher

as Lieutenant

Ben Corbett

as Sergeant