 Head coach Mike Smith named Grimes and Chris Houston the starting cornerbacks to begin the regular season.On November 22, 2009, Grimes collected a season-high ten combined tackles (eight solo), two pass deflections, and an interception during a 34–31 loss at the New York Giants.In Week 15, he recorded six solo tackles, deflected two passes, and intercepted two pass attempts by quarterback Mark Sanchez in the Falcons' 10–7 victory at the New York Jets.