In 1998, he won some cult and critical acclaim for his film Blood, Guts, Bullets and Octane which premiered in September 1997 at the New York Independent Feature Film Market and later at the 1998 Sundance Film Festival.
He directed the 2002 Detroit-set thriller Narc, starring Ray Liotta and Jason Patric. Following Narc, he directed an entry in the BMW Films titled Ticker starring Clive Owen and Don Cheadle. At one point he was solicited to direct Mission: Impossible III, produced by Tom Cruise and Paula Wagner (who also executive produced Narc), however, he subsequently left the production due to conflicting views on the tone of the film. It was also announced in October 2005, Carnahan would be directing a film based on the life of convicted drug dealer Will Wright, but the project seems to be abandoned.
His next film, Smokin' Aces, was produced in 2006 and released in January 2007. He also co-wrote the screenplay of Pride and Glory, released in 2008, nearly a year behind schedule.
He was attached to direct an adaptation of James Ellroy's novel White Jazz with George Clooney producing and starring, but Clooney later pulled out from the production and in 2009, Ellroy stated that all adaptations of the film were dead.[4]
In 2007, Carnahan penned Remarkable Fellows for Universal with Jason Bateman set to star,[5] but the film never went into production.
Carnahan was one of the executive producers for NBC's The Blacklist, starring James Spader and Megan Boone, during its first season. He directed the pilot, and went on to co-write and direct the ninth episode, "Anslo Garrick". Carnahan also wrote the story for episode 16, "Mako Tanida".
He is currently writing the script for the film adaptation of the Mark Millar comic book series Nemesis with his brother Matthew and will be directing.[8][9] He is also set to direct Mark Bowden's book Killing Pablo.[10]
Carnahan executive produced the NBC political thriller State of Affairs, starring Katherine Heigl and Alfre Woodard, which premiered November 17, 2014. He directed and co-wrote the pilot.
In June 2023, Carnahan is filming an adaptation of the non-fictional book, Not Without Hope by Nick Schuyler and Jeré Longman, a survival thriller starring Zachary Levi and Josh Duhamel.
On June 18, 2024, it was announced that Carnahan would write and direct the crime thriller RIP, starring Ben Affleck (who had previously worked with Carnahan on Smokin' Aces) and Matt Damon, with the project to be produced by Affleck and Damon's Artists Equity.[12] On July 2, it was announced that the project had been acquired by Netflix.[13]