Godbeer made his professional MMA debut on 7 August 2009 with a TKO victory over Sam Hooker. While fighting for numerous regional promotions, he amassed a record of 7-1 with all victories coming by way of knockout or submission. Following this, he was signed by BAMMA in 2012 to compete in their heavyweight division.
Between March 2012 and May 2016, Godbeer would remain undefeated in the BAMMA cage. During this time, he also signed on with Bellator MMA and would make a single appearance for the promotion, facing notable heavyweight Cheick Kongo on 4 October 2013 at Bellator 102. Following that loss, Godbeer would claim three straight victories in BAMMA, including winning the heavyweight title against Paul Taylor on 13 June 2015. During this run he would announce a brief retirement from MMA due to injury, but ended that retirement in May 2016 to defend the BAMMA heavyweight title.
Godbeer signed with the UFC in September 2016. He made his promotional debut on 19 November 2016 against Justin Ledet at UFC Fight Night 99. He would lose the bout via submission in the first round. Godbeer was expected to face Todd Duffee on 4 March 2017, at UFC 209. However, Duffee pulled out of the fight in mid-February for undisclosed reasons. He was replaced by promotional newcomer Daniel Spitz. Godbeer got his first ufc win under coach Brian Martin Gallacher and the Scottish hit squad team by unanimous decision. Godbeer was expected to face Walt Harris on 7 October 2017 at UFC 216 before a fight-day injury to Derrick Lewis took him out of his scheduled fight with Fabricio Werdum. As a result, Harris was moved on to face Werdum, and Godbeer was pulled from the event. The bout with Harris was rescheduled for 4 November 2017 at UFC 217. Godbeer won the fight via disqualification after Harris hit Godbeer with a head kick following the referee called a time out due to a groin strike. Godbeer was expected to face promotional newcomer Dmitry Poberezhets on 17 March 2018 at UFC Fight Night 127. However, it was announced on 25 January 2018 Poberezhets was injured and he was replaced by Dmitriy Sosnovskiy. Godbeer lost the fight via submission in the second round. Godbeer was briefly scheduled to face Luis Henrique in his return to light heavyweight division on September 22, 2018 at UFC Fight Night 137. However, Godbeer pulled out of the fight in early August citing injury and was replaced by promotional newcomer Ryan Spann. On September 25, 2018, Godbeer announced his retirement.
Bare-Knuckle Boxing
Mark Godbeer, while retired from MMA, transitioned over to bare-knuckle boxing and entered Ken Shamrock's newly founded Valor Bare Knuckle for its debut event, VKB: 1. Godbeer knocked out former fellow UFC, Bellator, & BAMMA veteran Jack "The Outlaw" May. Goddbeer knocked May out in less than a minute. He then faced current Road FC Open-weight Champion Mighty Mo in the main event for the tournament championship. Godbeer defeated Mo when after a series of punches Mo was knocked down and unable to get up in time for the 10 count, winning the VKB tournament.
