On March 17, 2010, Dunlap attended Florida's pro day and chose to perform multiple combine drills again.

At the conclusion of the pre-draft process, Dunlap was projected to be a second round pick by NFL draft experts and scouts.

[17] Throughout training camp, Dunlap competed to be a backup defensive end against Jonathan Fanene and Frostee Rucker.

Head coach Marvin Lewis named him the fifth defensive end on the depth chart to begin the regular season, behind Robert Geathers, Antwan Odom, Frostee Rucker, and Jonathan Fanene.

On September 26, 2010, Dunlap made his professional regular season debut during the Bengals' 20–7 victory at the Carolina Panthers in Week 3.

During the game, he made his first career tackle on running back Jason Snelling to stop a four-yard gain in the fourth quarter.

[20] Dunlap was elevated on the depth chart after Antwan Odom was suspended and Johnathan Fanene and Frostee Rucker sustained injuries.

[23][24] 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.

[25] 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.

[26] 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.

[28] During training camp, Dunlap competed to be a starting defensive end against Robert Geathers, Frostee Rucker, and Michael Johnson.

In Week 17, Dunlap collected a season-high six combined tackles and was credited with half a sack during a 24–16 loss to the Baltimore Ravens.

[31] During training camp, Dunlap competed to be a starting defensive end against Michael Johnson, Jamaal Anderson, and Derrick Harvey.

[32] Head coach Marvin Lewis named Dunlap the backup defensive end to begin the season, behind Robert Geathers and Michael Johnson.

[33] Dunlap sustained a knee injury during the preseason and was unable to play in the first two games of the regular season (Weeks 1–2).

[39] In week 13 against the New York Jets, Dunlap sacked quarterback Sam Darnold three times as the Bengals won their first game of the season 22–6.