The former 'Prison Break' star will play Antonius, the minister to Donald Sutherland's scheming leader, President Snow, for the upcoming third and fourth movies of the series, 'The Hunger Games: Mockingjay Parts 1 & 2', reported Entertainment Weekly.
The movies will be based on Suzanne Collins' final book in the bestselling series' trilogy, but the character is nowhere to be found in the novel.
Lionsgate bosses' have declined to comment on the development, and no other official information has been released.
Knepper will make his debut alongside fellow new cast members Julianne Moore, 'Game of Thrones' star Natalie Dormer, and Australian actress Stef Dawson, while Jennifer Lawrence, Josh Hutcherson, Liam Hemsworth and director Francis Lawrence all return for 'Mockingjay Part 1', due out next year.