The filmmaker recently entered talks to play a villain in the latest big screen instalment based on Tom Clancy's Jack Ryan novels.
Branagh confirmed his role while speaking at a Wallander III panel at the Television Critics Association presentation in Beverly Hills, reports Deadline.
He has already signed up to direct the thriller, which will feature Star Trek's Chris Pine in the leading role.
Speaking about the movie, Branagh said that it is "an original story that allows us to understand how Jack Ryan, created by Tom Clancy, develops into a CIA analyst, so this is before joining - perhaps even joining the CIA".
He added: "It's a very contemporary action thriller, set in the here and now."
Branagh will play Viktor Stazov, who creates a plot to destroy the US economy via the Russian government.
The currently-untitled Jack Ryan film is expected to enter production later this year.