The series, which was created by Spooks writer Neil Cross, will be fronted by former The Wire star Idris Elba.
Other actors announced as part of the cast include Ruth Wilson, Steven Mackintosh, Indira Varma, Warren Brown and Saskia Reeves.
McGann will play Mark North, a rival to Luther (Elba) who is competing for the affections of Zoe (Varma).
"Neil Cross's new series takes a bold new look at the detective show with great characters and intense psychological drama," said BBC controller of series and serials Kate Harwood.
"I'm delighted we've attracted such a strong cast to bring these characters to life."
The six-part series is scheduled to transmit on BBC One in 2010.