Oezdemir started as a professional mixed martial artist in 2010, with an overall record score of 9–0. He then signed a contract with 'The Bellator MMA' (also 'Bellator Fighting Championships'), the American mixed martial arts promotion. He made his promotional debut at 'Bellator 105' (the ninth season) on October 25, 2013, registering a victory via a first-round technical knockout against Josh Lanier.
On April 4, 2014, Oezdemir faced Kelly Anundson of the light heavyweight division at 'Bellator 115,' aired live on 'Spike TV.' Unfortunately, he was knocked out through a neck crank submission in the second round.
Oezdemir joined ‘UFC' after signing a contract in 2017. He made his promotional debut on February 4, 2017, at the event 'UFC Fight Night 104.' He, however, was a short-notice injury replacement and faced Ovince St. Preux, defeating him via a split decision in the third fight.
On May 28, 2017, he faced Misha Cirkunov in his second fight at the event 'UFC Fight Night 109' and registered a victory via a knockout within the first 28 seconds of the first round.
He then defeated the third-ranked ‘UFC’ light heavyweight fighter Jimi Manuwa at 'UFC 214' on July 29, 2017, by another knockout. He finished the match in the opening minute. He received a “Performance of the Night” bonus for his performance in the event.
On January 20, 2018, he lost to the heavyweight and light heavyweight world champion, Daniel Cormier, at 'UFC 220,’ via a technical knockout in the second round.
Oezdemir, who was supposed to fight Maurício Rua at 'UFC Fight Night 129,' on May 12, 2018, failed to participate in the event due to some visa-related issues that prevented him from traveling to Chile, as reported on April 13, 2018. He had to eventually withdraw from the event.
Nevertheless, the two faced each other in the ring on July 22, 2018, at 'UFC Fight Night 134.' Moreover, his fight against Alexander Gustafsson was rescheduled to August 4, 2018, at 'UFC 227,' as reported on July 2, 2018. Unfortunately, he was removed from the bout due to a nose injury.
Oezdemir lost the fight against Anthony Smith on October 27, 2018, at 'UFC Fight Night 138,' through a rear-naked choke submission in the third round. He lost to Dominick Reyes on March 16, 2019, at 'UFC on ESPN+ 5' via a controversial split decision.
On May 30, 2019, it was reported that Ilir Latifi, who was supposed to face Oezdemir at 'UFC Fight Night 153,' on June 1, 2019, had been removed due to his back injury and that the bout was canceled. The pair, however, faced each other at 'UFC on ESPN 5' on August 3, 2019.
The bout was shifted to 'UFC on ESPN+ 14,' as Oezdemir's visa to the United States had been rejected. He registered a victory via a knockout in the second round and bagged the “Performance of the Night” award.
Oezdemir defeated Aleksandar Rakić via a split decision at 'UFC on ESPN+ 23,' on December 21, 2019.
Oezdemir also has a record of 5–0 to his name in professional kickboxing. He made his debut in the sport in 2014, through 'SUPERKOMBAT,' the largest kickboxing organization in Europe.
On November 19, 2017, Oezdemir was charged with aggravated battery and arrested in Fort Lauderdale. He received bail in exchange for $10,000. On August 12, he caused physical harm to the alleged victim, Kevin Cohen. According to the fighter's manager, the physical altercation had taken place at a bar called 'Capone's.'
He was supposed to be sentenced to a maximum of 15 years in prison. However, on July 9, 2018, the charges on him were dropped. Oezdemir had been training with 'Combat Club' in South Florida during that time.