Weichel made his professional MMA debut in May 2002. Over the next four and a half years of his career, he amassed a record of 15-2. During this time, Weichel competed on a German mixed martial artsreality show titled M.A.X. in 2006, where he made it to the final against Ivan Mussardo. However, the production shut down before the match could actually take place. The two did eventually meet in 2009, where Weichel won by unanimous decision.
M-1 Global
Following a rough patch where he went 3-4, Weichel joined the Russian MMA organization M-1 Global, going 5-0 on their M-1 Challengers series. Weichel eventually challenged for the M-1 Global Lightweight Championship as he faced Jose Figueroa in November 2011 at M-1 Global: Fedor vs. Monson. He won the bout and title via knockout in the first round. Weichel's reign as champion would be short lived though. He lost the belt in his first defense in June 2012 against Musa Khamanaev at M-1 Global: Fedor vs. Rizzo. He lost the bout via submission in the first round.
In September 2013, it was announced that Weichel had signed a contract with Bellator MMA and would compete in their Season Ten Featherweight Tournament. Weichel made his Bellator debut in the Season Ten Featherweight Tournament Quarterfinal facing Scott Cleve at Bellator 110 on February 28, 2014 he won via submission with a rear-naked choke. Weichel fought against Matt Bessette at Bellator 114 on March 28, 2014 in the Featherweight tournament Semifinals. He won the bout via unanimous decision. Weichel faced Desmond Green in the Tournament Final at on May 9, 2014. He won the fight via submission in the second round. He also became the final tournament winner as Bellator moves away from tournament era. Weichel faced Pat Curran on February 13, 2015 at Bellator 133. He won the fight via split decision. Replacing an injured Georgi Karakhanyan, Weichel is scheduled to face Bellator Featherweight ChampionPatrício Freire at Bellator 138 on June 19, 2015. Despite dropping Freire with a series of strikes the waning seconds of the first round, Weichel lost the fight via knockout when Freire rallied with a counter left hook early in the second round. Weichel faced Georgi Karakhanyan at Bellator 147 on December 4, 2015. He won by unanimous decision. Weichel next faced up-and-comer Emmanuel Sanchez at Bellator 159 on July 22, 2016. He won via split decision. Weichel faced Brian Moore at Bellator 169 on December 16, 2016. He won the fight via submission in the first round. Weichel faced John Teixeira at Bellator 177 on April 14, 2017. He won via split decision. After four consecutive victories, Weichel was expected to face newly crowned featherweight champion, Patrício Freire, in a second fight at Bellator 188 on November 16, 2017. However, Freire pulled out of the fight due to multiple injuries. Weichel eventually faced Patricio Freire in a rematch in the main event at Bellator 203 on July 14, 2018. He lost the back-and-forth fight via split decision. After the title fight, Weichel faced Goiti Yamauchi at Bellator 210 on November 30, 2018. He lost the close fight via split decision.
As the opening round fight of the Grand Prix, Weichel faced Saul Rogers at Bellator 228 on September 28, 2019. Weichel won the fight via unanimous decision as he rocked Rogers late in the opening round. In the quarterfinals, Weichel was initially expected to face Emmanuel Sanchez in a rematch in February 2020. However, the date got pushed back and they were next expected to face at Bellator 241 on March 13, 2020. However, the whole event was eventually cancelled due to the prevailing COVID-19 pandemic.
