The film, adapted from a book by Joseph Kanon, will be directed by Steven Soderbergh for Warner Bros.
The drama follows an American journalist (Clooney) who gets involved in a murder mystery in Berlin after the war. He also finds himself falling in love.
Maguire will play a seemingly innocent soldier who drives the journalist around town, but has a secret plan of his own.
The Good German will be filmed in black and white, and production is scheduled to begin in the fall.