Magny began competing in MMA professionally in 2010, making his debut August 7, 2010 against Nolan Norwood for the C3 Fights promotion. Magny won the fight via submission (kimura) midway into the second round. Just a few months later Magny again fought for the C3Fights promotion, fighting against Nate Pratt, winning the fight via unanimous decision. Three weeks after his second win, Magny traveled to Indiana to fight for Cut Throat MMA on their November 6 card. Magny defeated Lawrence Dunning via TKO.
Magny won two more fights, bringing his overall record to 6-0, before being invited to compete in Combat USA's Wisconsin vs. Illinois championship series. Magny won his first round fight against fellow Illinois native, Quartus Stitt, via submission (triangle choke). The win moved Magny into the final round of the welterweight division tournament against a Wisconsin fighter. The final round took place on July 21, 2011 where Magny fought against Andrew Trace. Magny lost the fight via submission, marking the first time Magny had lost in his career.
Magny faced Seth Baczynski on November 6, 2013 at UFC Fight Night 31. He lost the back-and-forth fight via unanimous decision.
Magny next fought william Macário at UFC 179. He defeated Macário by TKO in the third round, his fifth UFC win of 2014.
Just 22 days after his loss to Maia, Magny stepped in as a short notice replacement for Rick Story to face Erick Silva on August 23, 2015 at UFC Fight Night 74. He won the fight via split decision.
Magny faced Johny Hendricks on December 30, 2016 at UFC 207. At the weigh-ins, Hendricks missed weight for their bout, weighing in at 173.5 lbs. As a result, Magny received 20% of Hendricks' purse and the bout was made a catchweight fight. Magny won the fight via unanimous decision.
Magny faced Carlos Condit on December 30, 2017 at UFC 219. He won the fight by unanimous decision.
Magny is expected to face Gunnar Nelson on May 27, 2018 at UFC Fight Night 130.