Dunlap was inactive as a healthy scratch for the first two games of the regular season. On September 26, 2010, Dunlap made his professional regular season debut during the Bengals' 20–7 victory at the Carolina Panthers in Week 3. Dunlap was inactive for another two games (Weeks 4–5), but made his return in Week 7 during a 39–32 loss at the Atlanta Falcons. During the game, he made his first career tackle on running back Jason Snelling to stop a four-yard gain in the fourth quarter. Dunlap was elevated on the depth chart after Antwan Odom was suspended and Johnathan Fanene and Frostee Rucker sustained injuries. Fanene, Odom, and Rucker were all placed on injured reserve where they would end the season. On November 14, 2010, Dunlap recorded two solo tackles and made his first career sack during a 23–17 loss at the Indianapolis Colts in Week 10. Dunlap made his first career sack on quarterback Peyton Manning for a four-yard loss in the second quarter. In Week 14, he collected a season-high four combined tackles and was credited with half a sack in the Bengals' 23–7 loss at the Pittsburgh Steelers. On November 25, 2010, Dunlap made three solo tackles and had two sacks on quarterback Mark Sanchez during a 26–10 loss at the New York Jets in Week 12. His earned his first multi-sack performance of his career with his two sacks. Dunlap finished his rookie season in 2010 with 24 combined tackles (19 solo), 9. 5 sacks, and three pass deflections in 12 games and zero starts. His 9. 5 sacks led the team and set a franchise record for most sacks by a rookie.