Martin-Green will play a lieutenant commander on the Discovery.
(CBS Television Studios had no comment.)
The casting brings the 31-year-old Martin-Green back to the CBS family.
Credit: Amanda Edwards/WireImage
She also starred as Tamara on ABCsOnce Upon a Time.
Martin-Greens husband, Kenric Green, is also an actor onTWD.
The series will also have the TV franchises first openly gay character, a lieutenant played by Anthony Rapp.
Fuller described Martin-Greens character as a lieutenant commander with caveats.
Weve seen six series from the captains point of view, he explained.
