Tibau made his UFC debut at welterweight against Nick Diaz. Tibau started strong and was taking Diaz down efficiently while avoiding submissions using Brazilian Jiu Jitsu. In the second round he got tired and lost by TKO due to strikes. Tibau took on Jason Dent at UFC 68. Tibau won by unanimous decision. He then took a one fight hiatus from the company and returned to defeat Jeff Cox by submission due to an arm-triangle choke. Tibau then fought undefeated Brit Terry Etim, outwrestling his opponent for a unanimous decision. Tibau then lost back to back fights to Tyson Griffin at UFC 81 and Joe Stevenson at UFC 86. He was on the verge of release from UFC by president Dana White. He rebounded with back to back wins over Rich Clementi and Jeremy Stephens. At the TUF 9 Finale, Tibau fought Melvin Guillard. Tibau lost by split decision. Many thought Tibau won the fight. Tibau's next fight was at UFC 104 where Tibau beat Josh Neer after landing 10 takedowns via unanimous decision. Tibau won his second straight match with a first round TKO over Caol Uno on March 31, 2010 at UFC Fight Night 21. Tibau faced Jim Miller on September 15, 2010 at UFC Fight Night 22. He lost the fight via unanimous decision. Tibau beat Kurt Pellegrino on March 19, 2011 at UFC 128 via split decision. Tibau then defeated veteran Rafaello Oliveira via second round rear naked choke, earning Submission of the Night honors. Tibau won via split decision against Rafael dos Anjos on November 19, 2011 at UFC 139. Tibau next faced undefeated prospect Khabib Nurmagomedov on July 7, 2012 at UFC 148, losing via unanimous decision. Tibau fought Francisco Trinaldo on October 13, 2012 at UFC 153 winning via unanimous decision. He lost to Evan Dunham on February 2, 2013 at UFC 156 by split decision. Tibau then faced John Cholish on May 18, 2013 at UFC on FX 8, winning via second round submission. Tibau beat Jamie Varner on August 31, 2013 at UFC 164 by split decision. With this fight, he became the youngest fighter in UFC history to record 20 bouts. Tibau lost to Michael Johnson in the last fight of his contract on December 28, 2013 at UFC 168 via second round knockout. On January 16, 2014, Tibau signed a four-fight contract. Tibau faced Pat Healy on July 16, 2014 at UFC Fight Night 45, winning by unanimous decision. Tibau next faced Piotr Hallmann on September 13, 2014 at UFC Fight Night 51. He won the back-and-forth fight via split decision. This fight earned Tibau his first Fight of the Night bonus award. Following the bout Hallmann failed his post fight drug test due to the presence of drostanolone in his system. Tibau defeated Norman Parke on January 18, 2015 at UFC Fight Night 59, replacing Jorge Masvidal, winning via split decision. Tibau replaced an injured Yancy Medeiros was against Tony Ferguson on February 28, 2015 at UFC 184, losing by submission in the first round, his first submission defeat since his 2008 loss to Joe Stevenson. Tibau smashed Abel Trujillo at UFC Fight Night 77 on November 7, 2015 via a first round submission. Tibau took Trujillo's back, secured a body triangle from the bottom and grabbed a rear-naked choke grip with his arm underneath Trujillo's chin. After a few seconds in this position, referee Keith Peterson halted the contest as he believed that Trujillo was unconscious. Trujillo indicated that he planned to appeal the decision in hopes that the result may be changed to a No Contest. On December 4, 2015, Tibau was suspended by USADA due to a potential Anti-Doping Policy violation stemming from an out-of-competition test. On December 23, 2015, it was reported that he had also failed an in-competition test following his win over Trujillo. On February 18, 2016 Tibau was suspended for 2 years by USADA as well as having the result of his fight against Trujillo reversed to a loss. Tibau faced Islam Makhachev on January 20, 2018 at UFC 220. He lost the fight by knockout in the first round. Tibau faced Desmond Green on June 1, 2018 at UFC Fight Night 131. He lost the fight by unanimous decision. Tibau's bout with Green marked the last fight of his contract and after more than a decade in the UFC, Tibau chose not to renew the contract, becoming a free agent.
Post-UFC career
After the long career in the UFC, Tibau revealed he will be moving up to welterweight division. On September 4, 2018, it was revealed that Tibau would fight Golden Boy Promotions' inaugural MMA event, headlined by the third encounter of Chuck Liddell and Tito Ortiz. Despite the announcement on going up a weight class, Tibau faced fellow UFC veteran Efrain Escudero in a 160lbs catchweight bout. He won the fight via unanimous decision. Tibau replaced Abel Trujillo on short notice against Will Brooks at Battlefield FC 2 on July 27, 2019 winning by Round 1 Submission.
