Phifer, 30, is already a veteran actor with nearly two dozen film credits, and is just finishing up his directorial debut, "Easier, Softer Way," MTV.com reported Friday.
The comedy stars Danny Masterson, Ronnie Warner and John C. McGinley in the tale of two stoners who take on Mr. Big.
Phifer said he is "very excited" about the Green project since he has long been an "avid fan" of his music.
The star of NBC's "ER" said he has already been working with the soul singer in preparation for the film.
"(Green) has full confidence, and he's like, 'Just do me right,'" Phifer told MTV. "We're just creating the story that we're going to show to the public, because it's so much, and obviously he's still alive. So it's just finding the right story that has the most impact."