 After missing the majority of the previous season due to injury, Mercilus finished the 2018 season with 39 tackles, four sacks, and two forced fumbles in all 16 games played.In the Wild Card Round of the playoffs against the Indianapolis Colts, Mercilus recorded one tackle in the 21–7 loss.In the season-opener against the New Orleans Saints, Mercilus sacked and intercepted Drew Brees in the narrow 30–28 road loss.