Sell was then seen as a middleweight contestant on The Ultimate Fighter: The Comeback, which premiered on August 17, 2006. He entered the competition alongside Matt Serra, who competed one weight class below Sell in the welterweight division. Sell defeated "Chainsaw" Charles McCarthy to move on the the semi-finals of the competition, where he lost to the ultimate winner of the tournament; Travis Lutter. Although Sell did not proceed the finals, he was featured on the undercard of the season finale where he lost to Scott Smith by knockout.
His second to last fight was a loss to Thales Leites at UFC 69. His last fight was a rematch against Nathan Quarry, at UFC Fight Night 11. Sell lost the fight by KO(Punch).
Pete made his second appearance on The Ultimate Fighter as a trainer for Team Serra for season 6, The Ultimate Fighter: Team Hughes vs. Team Serra.
| Result | Record | Opponent | Method | Event | Date | Round | Time | Location |
|---|---|---|---|---|---|---|---|---|
| Loss | 7-4 | Nathan Quarry | KO (Punch) | UFC - Fight Night 11 | 3 | 0:44 | Nevada, United States | |
| Loss | 7-3 | Thales Leites | Decision (Unanimous) | UFC 69 - Shootout | 3 | 5:00 | Texas, United States | |
| Loss | 7-2 | Scott Smith | KO (Punch) | The Ultimate Fighter 4 Finale | 2 | 3:25 | Nevada, United States | |
| Win | 7-1 | Landon Showalter | Decision (Unanimous) | ROC 10 - Ring of Combat 10 | 3 | 5:00 | The Tropicana, Atlantic City, NJ | |
| Loss | 6-1 | Nathan Quarry | TKO (Strikes) | UFC - Ultimate Fight Night | 1 | 0:42 | Nevada, United States | |
| Win | 6-0 | Phil Baroni | Submission (Guillotine Choke) | UFC 51 - Super Saturday | 3 | 4:19 | Nevada, United States | |
| Win | 5-0 | Chris Liguori | Submission (Rear Naked Choke) | ROC 6 - Ring of Combat 6 | 3 | 0:41 | New Jersey, United States | |
| Win | 4-0 | Chris Liguori | Decision (Split) | ROC 4 - Ring of Combat 4 | 3 | 5:00 | New Jersey, United States | |
| Win | 3-0 | Derek Johnson | Submission (Armbar) | ROC 3 - Ring of Combat 3 | 1 | 2:03 | New Jersey, United States | |
| Win | 2-0 | Ted Govola | Decision | ROC 2 - Ring of Combat 2 | 1 | 10:00 | New Jersey, United States | |
| Win | 1-0 | Rob Biegley | Decision | VATV 14 - Vengeance at the Vanderbilt 14 | 1 | 10:00 | New York, United States | |