The six-part series, which has been written by Hugo Blick, focuses on a group of individuals who become connected when drug baron Harvey Wratten is murdered.
The characters, including a police officer with amnesia and a drug lord, will all be affected by Wratten's death and will be forced to choose between right and wrong.
Chiwetel Ejiofor, who starred in American Gangster, and Doctor Who's Christopher Eccleston have both signed up to appear in the drama alongside Sir Anthony Sher and Stephen Rea.
The cast also includes Lesley Sharp, Desperate Romantics's Rafe Spall, Five Daughters star Kierston Wareing and Shameless's Sean Gilder. Freddie Fox, who appeared in Worried About The Boy, has joined the drama along with Malcolm Storry, Richard Lintern and David Schofield.
The BBC's controller of drama commissioning Ben Stephenson said: "As we continue our drive to build a bold and exciting drama story on BBC Two with commissions like Crimson Petal and The Hour, I am thrilled that we have attracted such world-class talent to Hugo Blick's thrilling scripts. Chiwetel and Chris are two of our finest actors and we couldn't be more excited to have them, and the rest of the amazing cast, on board for this original and epic six-hour series."
Filming for The Shadow Line will begin this month and the series is expected to air next year.