With his base in wrestling, he later started Brazilian jiu-jitsu and quickly earned a brown belt under Fábio "Pateta" Prado.

Faber made his professional MMA debut as part of the Gladiator Challenge promotion on November 12, 2003, defeating Poes Manne by a guillotine choke at 1:22 of round 1.

Faber then defeated George Adkins by TKO (strikes) on February 12, 2004, earning a shot at GC Bantamweight champion, David Velasquez.

Upon moving to KOTC, Faber defeated Rami Boukai by majority decision on September 24, 2004, barely a month after his last fight.

On March 13, 2005, Faber made his return to GC, defeating David Granados by rear naked choke at 2:13 of round 1.

Faber then fought at a TKO Major League MMA event on January 8, 2006, facing Ivan Menjivar.

On March 17, 2006, Faber competed for the first time in the World Extreme Cagefighting promotion, beating Cole Escovedo by second-round doctors stoppage and winning the WEC Featherweight Championship.

[10] On May 13, 2006, he fought for the King of the Cage Bantamweight Championship for the third time, defeating Charlie Valencia by rear naked choke submission at 3:09 of the first round.

Faber then took a fight in the Full Contact Promotions organization on September 9, 2006, defeating Enoch Wilson by TKO (strikes) at 1:01 of the second round.

On October 28, Faber returned to KOTC and defended his title for the fourth and last time, defeating future DREAM and ONE FC champion Bibiano Fernandes by TKO (cut) at 4:16 of round 1.

Cope on January 20, 2007, Faber defended his WEC Featherweight Championship for the first time since winning it ten months prior, defeating Joe Pearson by submission (strikes) at 2:31 of the first round.

In his post-fight interview, Faber called out K-1 Hero's 2005 Middleweight Tournament Champion Norifumi Yamamoto, though the fight never materialized.

Faber was next scheduled to fight Mike Brown at WEC 36 on September 10, 2008, at the Seminole Hard Rock Hotel & Casino in Hollywood, Florida.

Post-fight, Faber addressed WEC Featherweight Champion Mike Brown, who was seated at ringside and announced he wanted a shot at regaining his title.

[14] When Brown made his first successful title defense at WEC 39 in Corpus Christi, Texas, he responded to Faber's comments by saying that a rematch between the two of them was something "the fans want to see.

"[15] Faber was defeated a second time by Mike Brown at WEC 41 on June 7, 2009, by a unanimous decision (49–46, 49–46, and 48–47) in front of his hometown crowd in Sacramento.

Early in the fight, Faber broke his right hand and later dislocated his left thumb, resorting to using primarily elbows and kicks starting in the third round.

Sherdog and ESPN.com in a post-fight article noted that Faber's "right hand was no match for the top of Mike Brown's head."

[25][26] With the victory over Mizugaki, Faber won his ninth WEC bout, a promotional record he shares with Antonio Banuelos and Poppies Martinez.

[27] Faber made his promotional debut against former WEC Bantamweight Champion Eddie Wineland on March 19, 2011, at UFC 128.

[35][36] Following his win at UFC 139, Faber was selected to be a coach on The Ultimate Fighter: Live opposite Dominick Cruz.

[47] Despite being in trouble early in the first round, Faber recovered and used his wrestling and relentless top game, outstriking Alcântara 127 to 25 over the duration of the bout.

[51] When Dominick Cruz injured himself before his unification bout with Renan Barão, Faber was chosen as the replacement in the title fight at UFC 169.

Faber grabbed Barão's leg, and gave the referee the thumbs-up, indicating that he wanted the fight to continue.

[61] Rivera's management team indicated that they planned to appeal the result in hopes that it would be changed to a no contest, and that the UFC could schedule a rematch with Faber.

[64] However, Assunção was forced out of the bout as an ankle first injured in mid-December 2014 was slow to heal and that he was unable to resume the proper training to prepare for the fight in that time frame.

[79] In October 2016, Faber announced that his next fight, a bout against Brad Pickett on December 17, 2016, at UFC on Fox 22 in his home town of Sacramento would be his last.

[83] After two-and-a half years away from mixed martial arts competition, Faber made his return to the Octagon as he faced Ricky Simón on July 13, 2019, at UFC Fight Night 155.

[91] See Team Alpha Male In December 2021, Faber agreed on short notice to compete in his first Combat Jiu-Jitsu match against a CJJ world champion Elias Anderson, at the Featherweight edition of the CJJ world championships.,[92] but passport issues led to Faber being replaced by Erik Perez, who lost to Anderson.

[95] Faber returned to wrestling competition at the 2022 US Open alongside his teammate Clay Guida, coming away with a silver medal at the event.