
Smith defeated WEC veteran Tim McKenzie in the semi-finals. With that victory, Smith was slated to fight Justin Levens in the tournament finals; Levens, however, was halted on doctor's advice due to a shoulder injury he sustained in his semi-final bout. The tournament alternate, Tait Fletcher, was brought into the championship round instead. Smith made short work of Fletcher, scoring a first-round technical knockout to become the WEC Light Heavyweight Champion.
Smith would defend his championship from Justin Levens at WEC 18 before scheduling a fight with the Ultimate Fighting Championship in April of 2006, moving down a weight class to fight David Terrell at UFC 59. The fight – marked with questionable officiating – ended in controversial fashion, prompting Smith to file a complaint with the California State Athletic Commission. 
Smith was then seen as a middleweight contestant on The Ultimate Fighter: The Comeback, where he quickly lost his quarterfinal matchup against Travis Lutter. Smith appeared on the season finale, knocking out Pete Sell in the second round of a very exciting fight in a sequence that saw Smith sustain a hard punch to the liver, and throw the bout-winning knockout punch before falling to the ground in pain.
Smith lost his next fight in the UFC by decision against Patrick Cote at UFC 67.
More recently, Smith defeated Troy Miller by technical knockout at Palace Fighting Championship 2 in Lemoore, California. He lost against Ed Herman at UFC 72. Herman submitted Smith with a rear naked choke at 2:25 in the second round after Herman landed a nasty elbow on Smith in the first round covering his face in blood.
Smith made his EliteXC debut on February 16th knocking out Kyle Noke seven seconds into round two. The victory earned him a title shot against Robbie Lawler. The bout was declared a no contest after an accidental poke in the eye in the third round. The first two rounds were so exciting that Gary Shaw awarded both fighters their win bonuses and announced an immediate rematch. Smith lost the subsequent rematch to Lawler via TKO on July 26, 2008 at EliteXC: Unfinished Business.
| 13-5-0 (wins-losses-draws) | |||||||
| Loss | Robbie Lawler | TKO (Kicks and Punches) | EliteXC: Unfinished Business | 07/26/2008 | 2 | 2:35 | For EliteXC middleweight championship |
| NC | Robbie Lawler | No contest (Unintentional foul) | EliteXC: Primetime | 05/31/08 | 3 | 3:26 | For EliteXC middleweight championship |
| Win | Kyle Noke | KO | EliteXC: Street Certified | 02/16/08 | 2 | 0:07 | |
| Win | Jeff Morris | TKO | GC 73 - High Noon | 12/22/07 | 1 | 0:22 | |
| Loss | Ed Herman | Submission (Rear Naked Choke) | UFC 72: Victory | 06/16/2007 | 2 | 2:25 | |
| Win | Troy Miller | TKO | PFC 2 - Fast and Furious | 03/22/2007 | 1 | 1:06 | |
| Loss | Patrick Cote | Decision (Unanimous) | UFC 67: All or Nothing | 02/3/2007 | 3 | 5:00 | |
| Win | Pete Sell | KO (Punch) | The Ultimate Fighter 4 Finale | 11/11/2006 | 2 | 3:25 | |
| Loss | David Terrell | Submission (Rear Naked Choke) | UFC 59: Reality Check | 04/15/2006 | 1 | 3:08 | |
| Win | Justin Levens | KO | WEC 18 - Unfinished Business | 01/13/2006 | 1 | 1:58 | |
| Win | Tait Fletcher | TKO (Punches) | WEC 17 - Halloween Fury 4 | 10/14/2005 | 1 | 3:55 | Became WEC Light Heavyweight Champion |
| Win | Tim McKenzie | TKO (Punches) | WEC 17 - Halloween Fury 4 | 10/14/2005 | 1 | 2:25 | WEC Light Heavyweight Semi-finals |
| Win | John Seilhan | TKO | GC 30 - Gladiator Challenge 30 | 08/19/2004 | 1 | 1:29 | |
| Loss | James Irvin | KO | GC 22 - Gladiator Challenge 22 | 02/12/2004 | 1 | 2:21 | |
| Win | Jaime Jara | Submission (Rear Naked Choke) | GC 20 - Gladiator Challenge 20 | 11/13/2003 | 1 | 3:01 | |
| Win | Jaime Jara | KO | GC 16 - Gladiator Challenge 16 | 06/1/2003 | 1 | N/A | |
| Win | Levi Thornbrue | TKO | GC 10 - Gladiator Challenge 10 | 04/14/2002 | 1 | 2:20 | |
| Win | Tim Kennedy | TKO (Cut) | IFC WC 15 - Warriors Challenge 15 | 08/31/2001 | 1 | 2:53 | |
| Win | Ted Stamatelos | Submission | IFC WC 13 - Warriors Challenge 13 | 06/15/2001 | N/A | N/A | |