Hominick lost his first two WEC bouts back to back with first round submission losses to Rani Yahya and Josh Grispi at WEC 28 and WEC 32 respectively. He was scheduled to fight Deividas Taurosevičius on October 10, 2009 at WEC 43., but was forced to withdraw due to an injury and was replaced by Javier Vazquez. Hominick was scheduled to face Yves Jabouin on January 10, 2010 at WEC 46, but Jabouin was forced off the card with an injury. Hominick instead faced WEC newcomer Bryan Caraway, winning via first round submission. The fight eventually took place on June 20, 2010 at WEC 49. Hominick won via TKO in the second round. They both won a Sherdog award for best round of 2010. Hominick faced Leonard Garcia on September 30, 2010 at WEC 51. He won the fight via split decision.
Return to UFC
On October 28, 2010, World Extreme Cagefighting merged with the Ultimate Fighting Championship. As part of the merger, all WEC fighters were transferred to the UFC. Hominick faced former training partner, George Roop on January 22, 2011 at UFC Fight Night 23 in a top contender bout. Hominick stopped Roop via punches in the first round. Hominick faced UFC Featherweight ChampionJosé Aldo on April 30, 2011 at UFC 129, where he lost via unanimous decision in a bout that earned Fight of the Night honors. Hominick faced Chan Sung Jung on December 10, 2011 at UFC 140. Hominick attempted to recklessly attack Jung immediately after touching gloves and was dropped with a counter right. Jung followed up with punches until Hominick went limp and the referee brought an end to the fight, tying one of the fastest KOs in the UFC. Hominick faced Eddie Yagin on April 21, 2012 at UFC 145. Hominick lost the fight via split decision, in a bout that earned both participants Fight of the Night honors. Hominick faced Pablo Garza on November 17, 2012 at UFC 154. He lost the fight by unanimous decision. After the loss at UFC 154, Hominick announced his retirement on December 11, 2012, stating "I truly got to live my passion and follow my dreams by competing in mixed martial arts, especially under the Zuffa banner, but UFC 154, that's the last fight I'll be in the octagon, as I'm retiring and looking to move on to the next phase of my career."
Personal life
Hominick attended I.D.C.I school in Ingersoll, Ontario. Hominick married in December 2009. They have two children. Mark Hominick has been involved with several other UFC fighters as part of a Toronto area anti-bullying program.