Matthew grew up a 4th generation Californian, son of an Osage Nation mother and Irish-American father. He's worked in the circus, as a dancer, on boats, cooking in Idaho, Seattle and New York, and as a private chef on both coasts. After Attending the Neighborhood Playhouse under Sanford Meisner and the NYU MFA Tisch Program, he went on to write scripts for Tom Hanks and to adapt his play, The Knees of a Cellist for Francis Ford Coppola. He wrote and directed the short film, Mailman (1996), produced by Sandra Bullock, which premiered at The Sundance Film Festival, as did his feature directorial debut, Black Circle Boys (1997), to critical acclaim. Carnahan's documentary about former Mayor Rudolph Giuliani, Rudyland (2001), played IDFA Amsterdam and sold to HBO. His novel, Serpent Girl, was published by Random House in 2006 to rave reviews and three editions, which he has adapted into a series for ITV America. He's working on a new novel, I'm Letting You Go Now.