| Anna Torv | Olivia Dunham /
Alternate Olivia Dunham |
| Joshua Jackson | Peter Bishop |
| Jasika Nicole | Astrid Farnsworth |
| John Noble | Dr. Walter Bishop |
| Michael Cerveris | September |
| James Kidnie | The Commander |
| Michael Kopsa | Captain Windmark |
| Seth Gabel | Lincoln Lee |
| Lance Reddick | Phillip Broyles |
| Sarwan Badesha | Alt Universe Fringe Agent #2 |
| Natalie Edwards | Young Fringe Agent
(as Natalie Brooke Edwards) |
| Jonathan Fitzgerald | Observer #2 |
| Peter Flemming | Loyalist Lieutenant |
| Craig Fraser | Loyalist Guard #1 |
| Mackenzie Gray | Observer Physician #1 |
| Rustin Gresiuk | Trevor |
| Abagayle Hardwick | Young Etta |
| Simon Hill | Observer Surgeon |
| Peter Kelamis | Tobin |
| Eugene Lipinski | December |
| Rowan Longworth | Michael |
| Tara Pratt | Alt Universe Fringe Agent #1 |
| Ivan Wanis-Ruiz | Amon
(as Ivan Wanis Ruiz) |
| Jordan Schartner | Observer #1 |
| Lucas Wolf | Observer Physician #2 |
| Andrea Yu | Alt Universe Fringe Agent #4 |
| Vanessa Zachos | Loyalist Nurse |
| Eric Floyd | Observer
(uncredited) |