As was customary in his late Monogram westerns, Johnny Mack Brown plays an undercover agent in Colorado Ambush. Brown is sent to Colorado to stem the activities of a particularly vicious outlaw gang
| Actor | Role |
|---|---|
 Johnny Mack BrownJohnny Mack Brown | Johnny Mack Brown |
 Myron HealeyChet Murdock | Chet Murdock |
 Lois HallJanet Williams | Janet Williams |
 Tommy FarrellTerry Williams | Terry Williams |
 Christine McIntyreMae Star | Mae Star |
 Lee RobertsHenchman Gus | Henchman Gus |
 Marshall BradfordBen Williams | Ben Williams |
 Lyle TalbotSheriff Ed Lowery | Sheriff Ed Lowery |