Cast complete, awaiting verification
| Steve Coogan | ... | Self / Martin Sixsmith | |
| Judi Dench | ... | Self / Philomena | |
| Stephen Frears | ... | Self | |
| Jeff Pope | ... | Self | |
| Cathy Belton | ... | Sister Claire (archive footage) (uncredited) | |
 |
Tadhg Bowen | ... | Young Anthony (archive footage) (uncredited) |
| Nicholas Jones | ... | Dr. Robert (archive footage) (uncredited) | |
| Florence Keith-Roach | ... | Check In Operator (archive footage) (uncredited) | |
| Sophie Kennedy Clark | ... | Young Philomena (archive footage) (uncredited) | |
| Anna Maxwell Martin | ... | Jane (archive footage) (uncredited) | |
| Wunmi Mosaku | ... | Young Nun (archive footage) (uncredited) | |