Arnoux was drafted by the New Orleans Saints in the fourth round of the 2009 NFL Draft. In the first practice of Saints rookie minicamp, Arnoux tore his left Achilles tendon. He missed the entire 2009 season due to the severity of the injury. He was signed to a four-year contract on September 7, 2009 and immediately placed on injured reserve due to his injury. In 2010, he was on the active roster for the Saints' first 10 games, but suffered another Achilles tendon injury in a game against Seattle, and was placed on the injured reserve list on November 23, 2010.James Varney, "New Orleans Saints put linebacker Stanley Arnoux on injured reserve", Times-Picayune, November 23, 2010.
