 Head coach Joe Philbin named Grimes the starter to begin the regular season, alongside Dimitri Patterson.On September 15, 2013, Grimes recorded a season-high three pass deflections, five combined tackles, and intercepted a pass by Andrew Luck during a 24–20 victory at the Indianapolis Colts in Week 2.In Week 9, he collected five solo tackles, deflected a pass, and returned an interception for his first career touchdown in the Dolphins' 22–20 win against the Cincinnati Bengals.