Ultimate Fighting Championship
On February 24, 2009, it was announced on the official UFC website that Akiyama had signed a deal with the company. Akiyama made his debut against Alan Belcher at UFC 100 on July 11. Despite suffering a broken orbital, he won by split decision (30–27, 28–29, 29–28). It was the 1st fight in Akiyama's career that went to the judges' score cards. The bout was also awarded "Fight of the Night" honors, granting both fighters a record-setting $100,000 bonus each.
On May 30, 2009, Akiyama opened a new gym in Tokyo, Japan. The 'Akiyama Dojo' has Judo and MMA halls, 30 tatami mats and three octagonal cages.
Akiyama joined Xtreme Couture for the month of October 2009 to work on his striking skills. Akiyama was expected to face MMA legend and former PRIDE Middleweight Champion Wanderlei Silva on February 21, 2010, at UFC 110, but Silva instead faced British striker Michael Bisping on the card, winning via unanimous decision. At the Post-fight conference, UFC President Dana White stated that Akiyama had requested to fight Silva for a while and has refused to fight other opponents, after which both fighters verbally agreed to fight.
Akiyama was expected to face Silva on July 3, 2010, at UFC 116. Wanderlei had to pull out on June 22, 2010, due to fractured ribs suffered in training. Chris Leben was chosen as a replacement. Despite controlling the majority of the fight with effective strikes and solid Judo takedowns, Akiyama became fatigued after the first round and lost via triangle choke with just twenty seconds left in the third round. His loss to Leben was his first official loss in five years.
Akiyama lost to Michael Bisping on October 16, 2010, at UFC 120 by unanimous decision. In preparation for his fight with Bisping, Akiyama switched to Jackson's Submission Fighting in Albuquerque, New Mexico. It is unclear whether the switch is permanent. Even though Akiyama lost to Bisping, he rocked him in the first round. He earned his third "Fight of the Night" honors. He has now earned "Fight of the Night" honors for all three of his UFC appearances.
Akiyama was briefly scheduled to face Chael Sonnen on March 19, 2011, at UFC 128, but, due to Sonnen's suspension, the fight was scrapped. Akiyama was later scheduled to face Nate Marquardt at the same event, but pulled out due to the 2011 Tōhoku earthquake and tsunami and was replaced by Dan Miller.
Akiyama was defeated by Vitor Belfort at UFC 133 via KO (Punches) in the first round. This defeat marked the third straight loss for Akiyama in the UFC. Following the fight, Dana White stated that Akiyama most likely would not be cut from the organization if he agrees to move down to welterweight. As of September 3, 2011, Akiyama has stated he will move down a weight class, allowing him to stay in the UFC. On November 3, 2011, a picture of Akiyama had circled the web of his body frame as a welterweight.
Akiyama faced Jake Shields on February 26, 2012, at UFC 144. He lost the fight via unanimous decision (30–27, 30–27, 30–27). During the bout, Akiyama was able to utilize multiple judo techniques which was praised as the main highlights of the fight; despite losing the decision.
Akiyama was expected to face Thiago Alves on July 21, 2012, at UFC 149. However, Akiyama was forced out of the bout with an injury.
Akiyama had made an appearance alongside UFC featherweight Hatsu Hioki during the Q&A session for UFC on Fuel TV 8. During the Q&A, Akiyama stated he was thinking about returning for another bout as long as he has a free schedule as well as being matched against a well-known opponent that would interest fans. Akiyama also stated he still has interest in fighting Wanderlei Silva, a bout scheduled for UFC 116 but was changed when Silva had to pull out of the fight due to injury.
After over two and a half years away from the sport, Akiyama returned from his self-imposed hiatus on September 20, 2014, at UFC Fight Night 52. He was originally scheduled to face Kyle Noke on the card. However, Noke was forced out of the bout with a knee injury and replaced by Amir Sadollah. Akiyama won the fight via unanimous decision.
After another year away from the sport, Akiyama returned to face Alberto Mina on November 28, 2015, at UFC Fight Night 79. He lost the back-and-forth fight via split decision.