During the 2011 season, Edelman was used primarily as a kick and punt returner. During the Patriots' Week 10 game against the New York Jets, because of injuries to the Patriots' secondary, he was pressed into service as a defensive back during the fourth quarter; he earned his first tackle on defense by stopping running back LaDainian Tomlinson on a play in which Tomlinson injured his MCL.
During the Patriots' Week 11 game on Monday Night Football against the Kansas City Chiefs, he played defensive back in nickel and dime situations. He also returned a punt 72 yards for a touchdown, which helped him earn his first AFC Special Teams Player of the Week award. In Week 12 he was nominated for the NFL's "Hardest Working Man" for his Week 12 performance against the Philadelphia Eagles, in which he made an open-field tackle on Vince Young to prevent a touchdown.
In the AFC Conference Championship Game, on January 22, 2012, against the Baltimore Ravens, Edelman played on 27 of 67 offensive snaps at wide receiver, catching one pass that converted a third down attempt, and 27 of 73 defensive snaps at cornerback, often covering the Ravens' Anquan Boldin; Edelman was credited with a forced fumble on the Ravens' final drive.