| Roy Thinnes | David Vincent / ... (43 episodes, 1967-1968) |
| Hank Simms | Introductory Narrator / ... (43 episodes, 1967-1968) |
| William Woodson | Narrator (43 episodes, 1967-1968) |
| Kent Smith | Edgar Scoville / ... (13 episodes, 1967-1968) |
| Mark Russell | Alien / ... (4 episodes, 1967-1968) |
| Robert Dulaine | Alien / ... (4 episodes, 1967) |
| William Windom | Michael Tressider / ... (3 episodes, 1967) |
| Lin McCarthy | Colonel Archie Harmon / ... (3 episodes, 1967-1968) |
| Alfred Ryder | Mr. Nexus / ... (3 episodes, 1967-1968) |
| Michael Rennie | Vice Chancellor Pierre Alquist / ... (3 episodes, 1967) |
| Anthony Eisley | Bob Torin / ... (3 episodes, 1967) |
| Diana Hyland | Ellie Markham / ... (3 episodes, 1967) |
| John Milford | James Boland / ... (3 episodes, 1967-1968) |
| Richard O'Brien | Brother John / ... (3 episodes, 1967-1968) |
| Simon Scott | Dr. Ed Gantley / ... (3 episodes, 1967-1968) |
| Byron Keith | Air Crash Investigator / ... (3 episodes, 1967-1968) |
| John Ward | Alien Pilot / ... (3 episodes, 1967-1968) |
| Ray Kellogg | Guard / ... (3 episodes, 1967) |
| Wayne Heffley | Deputy / ... (3 episodes, 1967-1968) |
| Ross Elliott | Hotel Detective / ... (3 episodes, 1967-1968) |
| Morgan Jones | First Reporter / ... (3 episodes, 1967-1968) |
| Michael Harris | Mail Truck Driver / ... (3 episodes, 1967-1968) |
| Peter Mark Richman | Andrew Hatcher / ... (2 episodes, 1967-1968) |
| Linden Chiles | Dr. Robert A. 'Bob' Vincent / ... (2 episodes, 1967) |
| J.D. Cannon | Peter Kalter / ... (2 episodes, 1967-1968) |
| Joanne Linville | Angela Smith / ... (2 episodes, 1967-1968) |
| William Smithers | Adam Lane / ... (2 episodes, 1967-1968) |
| R.G. Armstrong | Gus Flagg / ... (2 episodes, 1967-1968) |
| Susan Oliver | Joan Seeley / ... (2 episodes, 1967-1968) |
| Suzanne Pleshette | Anne Gibbs / ... (2 episodes, 1967-1968) |
| Eduard Franz | Premier Thor Halvorsen (2 episodes, 1967) |
| Edward Asner | Harry Ferguson / ... (2 episodes, 1967-1968) |
| Donald Davis | Harland / ... (2 episodes, 1967-1968) |
| Patricia Smith | Edna Greely / ... (2 episodes, 1967) |
| Katherine Justice | Helen - Vincent's Girlfriend / ... (2 episodes, 1967-1968) |
| James T. Callahan | Dr. Harry Mills / ... (2 episodes, 1967) |
| Harold Gould | Allen Slater / ... (2 episodes, 1967) |
| Ed Begley | Dr. Samuel Crowell / ... (2 episodes, 1967) |
| Laurence Naismith | Cyrus Stone / ... (2 episodes, 1967) |
| James Daly | Alan Landers / ... (2 episodes, 1967-1968) |
| Dabney Coleman | Captain Mitchell Ross / ... (2 episodes, 1967) |
| Tim McIntire | Hal / ... (2 episodes, 1967) |
| Robert H. Harris | Bill Hastings / ... (2 episodes, 1967-1968) |
| Gene Lyons | John Corwin / ... (2 episodes, 1967-1968) |
| Douglas Henderson | Lieutenant Farley / ... (2 episodes, 1967) |
| Lawrence Montaigne | First Man / ... (2 episodes, 1967) |
| Ford Rainey | Dr. George Grundy / ... (2 episodes, 1967) |
| William Sargent | Dr. John Devin / ... (2 episodes, 1967) |
| Frank Marth | Alien #1 AKA Calvin Adams / ... (2 episodes, 1967) |
| Barney Phillips | Emmett Morgen / ... (2 episodes, 1967) |
| John S. Ragin | John Finney / ... (2 episodes, 1967) |
| Ross Hagen | Jorden / ... (2 episodes, 1967-1968) |
| Tom Palmer | Charlie Spence / ... (2 episodes, 1967) |
| Paul Comi | Danny - Sheriff / ... (2 episodes, 1967-1968) |
| Lew Brown | Aide / ... (2 episodes, 1967) |
| Robert Sorrells | Deputy Jim / ... (2 episodes, 1967) |
| Rayford Barnes | Alien Deputy / ... (2 episodes, 1967-1968) |
| Joel Fluellen | Butler Henry / ... (2 episodes, 1967-1968) |
| Johnny Jensen | Frankie Reed / ... (2 episodes, 1967-1968) |
| Noah Keen | Paul Meyers / ... (2 episodes, 1967-1968) |
| Christopher Shea | Boy - Jimmy / ... (2 episodes, 1967-1968) |
| John Zaremba | General / ... (2 episodes, 1967) |
| Mary Jackson | Hattie Willis / ... (2 episodes, 1967-1968) |
| Lee Farr | Justice Department Agent (2 episodes, 1967) |
| Robert Knapp | Congressman Joe Bonning / ... (2 episodes, 1967) |
| Byron Morrow | Col. Newcomb / ... (2 episodes, 1967) |
| Burt Douglas | Alien #1 / ... (2 episodes, 1967-1968) |
| Hal Baylor | Friendly Guard / ... (2 episodes, 1967) |
| Hank Brandt | Joe Manners / ... (2 episodes, 1967) |
| William Stevens | Cobbs / ... (2 episodes, 1967) |
| Sam Edwards | Hank / ... (2 episodes, 1967) |
| Tina Menard | Maid / ... (2 episodes, 1967) |
| Dallas Mitchell | Andy / ... (2 episodes, 1967) |
| William Wintersole | Alien in Charge / ... (2 episodes, 1967) |
| James Devine | Jimmy / ... (2 episodes, 1967-1968) |
| Troy Melton | Chauffeur / ... (2 episodes, 1967-1968) |
| Don Eitner | Townsman / ... (2 episodes, 1967) |
| Max Kleven | Guard #2 / ... (2 episodes, 1967) |
| Allen Emerson | Library Alien / ... (2 episodes, 1967) |
| John Mayo | Alien / ... (2 episodes, 1967) |
| David Armstrong | M.P. / ... (2 episodes, 1967) |
| Don Ross | Ed Larson / ... (2 episodes, 1967) |
| Dabbs Greer | The Minister (2 episodes, 1967) |
| Dan Frazer | Reporter (2 episodes, 1967) |
| Ted Knight | Alien Air Force Major McEvoy / ... (2 episodes, 1967) |
| Gilchrist Stuart | Reporter / ... (2 episodes, 1967) |
| Jason Wingreen | Court Clerk / ... (2 episodes, 1967) |
