In 2009, he finished with 41 tackles and 5.5 sacks. Avril continued improving in 2010, with 33 tackles and 8.5 sacks. In 2011, he appeared in all 16 games for the first time in his NFL career, finishing with 36 tackles, 11 sacks, six forced fumbles and three fumble recoveries, including one returned for a touchdown. He also returned an interception for a touchdown during the 2011 season. In March 2012, the Lions placed the franchise tag on Avril, keeping him in Detroit for one more season. He finished with 35 tackles, 9.5 sacks and two forced fumbles. In March 2013, Avril signed a two-year contract with the Seattle Seahawks. In his first season for Seattle, he appeared in 15 games, posting 20 tackles, eight sacks and five forced fumbles.