Aidan Gillen Joins FX’s Witness Protection Pilot Cast

LOS ANGELES, CA — Aidan Gillen has been cast as a key guest star in FX‘s upcoming pilot for an untitled Witness Protection series. This announcement was made on September 22, 2025, and it comes with the possibility for his role to expand if the show is picked up for a full series.

Gillen joins an already established lead cast that includes Alison Brie, Pablo Schreiber, Zoë Chao, Jamie Neumann, and Antonella Rose. The pilot is a contemporary take on a previously unproduced script by David Chase, known for creating The Sopranos.

In the series, Brie plays Remy, a high-end D.C. madam who turns against her partner after a violent incident. Seeking protection for herself and her adolescent daughter, she enters the Witness Protection Program in a coastal town in Maine.

Gillen will portray Carl Milliken III, a business executive more immersed in his work than the military contractors he interacts with. Schreiber plays a gun store owner who aids Remy, while Rose plays her daughter, Liv. Chao is cast as the mother of one of Liv’s friends, and Neumann appears as an escort in their new town.

The pilot is directed by Hannah Fidell, who co-writes and serves as showrunner alongside Gina Welch. Nicole Lambert also acts as an executive producer through Riverain Pictures.

Gillen is widely recognized for his roles in prominent shows like Game of Thrones, where he played Petyr “Littlefinger” Baelish, as well as his appearances in Mayor of Kingstown and Peaky Blinders. His other notable film credits include Bohemian Rhapsody and the Maze Runner series.

Production sources indicate excitement about Gillen’s involvement, particularly given his established reputation in the industry. His future projects include The Physician II and a WWII thriller titled The Duel.