The 'Treme' alum, 49, will play the female lead in the yet-to-be-titled series with the previously announced male lead Cliff Curtis, according to Variety.
Other actors booked for the show include Frank Dillane ('Harry Potter and the Half-Blood Prince') and Alycia Debnam-Carey ('The 100').
Often referred to as Cobalt, the show is set at the beginning of the same zombie apocalypse as the wildly popular original program. While 'The Walking Dead' takes place in Georgia, the upcoming companion series is expected to find itself in California.
Her character is tentatively named Nancy Tompkins, and is seeing Dillane's teacher character.