He is a frequent guest commentator and analyst on national radio and television programs, including MSNBC, the BBC, the CBC, and National Public Radio. His work was featured in the anthology The Best American Magazine Writing 2012.
Matthieu received the 2013 Polk Award for magazine reporting, the Medill Medal for Courage, and the Kurt Schork Award for his Rolling Stone article "The A-Team Killings," which uncovered evidence of war crimes in Afghanistan. He was a finalist for the National Magazine Award in the Reporting category for his 2011 article in the Atlantic, which exposed a massacre by Afghan security forces. In 2010, he won a National Magazine Award in Canada for 'Best New Creative Talent' for his article 'Last Stand in Kandahar', which appeared on the cover of the November issue of the Walrus. In 2008 and 2009 he also received prizes from the Canadian Association of Journalists and the Atlantic Journalism Awards.
Matthieu has a master's degree in Near Eastern Studies from New York University. His academic interests include the geopolitics of South and Central Asia, and the future of journalism and new media. On the latter subject, he worked with Jay Rosen and the innovative Studio 20 program at NYU. He currently splits his time between Afghanistan and Pakistan.