Clementi has fought for the Ultimate Fighting Championships, Bellator, K-1 Hero's DREAM, King of the Cage, and Titan FC.

Though he was a standout prep wrestler, Clementi joined the military out of high school and served in the United States Navy's Construction Battalion.

He appeared on the undercard of the season finale as a lightweight, but lost by rear naked choke submission to Din Thomas.

Clementi followed up with an appearance at UFC Fight Night: Lauzon vs. Stephens, where he lost to Gleison Tibau by guillotine choke.

On November 29, 2009, Clementi headlined the event "Cage Wars: Nightmare" in Belfast, Northern Ireland and fought local prospect Chris Stringer, defeating him by triangle choke in the second round, after dominating the fight.

[3] Clementi followed that win by headlining the Team 3:16 – Season's Beatings Event in Shreveport, Louisiana, defeating Derrick Krantz in the first round via armbar.

Clementi faced Alexander Sarnavskiy on October 19, 2012 at Bellator 77 in a Lightweight Tournament Quarter Final bout.

Clementi faced Marcin Held in the Semifinals on November 16, 2012 at Bellator 81 and lost via toe hold submission in the second round.