Glenn was born in Marshalltown, Iowa, an idyllic small town of Midwest America. With an adventure spirit, he had interest in BMX biking but the interest in fighting outweighed biking since he was young. He did a year of wrestling at Marshalltown High School and started boxing training when he was fourteen. He loved combat sport so much that when his local boxing gym closed down, he travelled one and half hour each trip to other gym to get his boxing practice. He later transitioned to MMA training at a friend's basement and switch to his uncle's garage. When Glenn was seventeen, still a high school student and with one year wrestling, some boxing experience and self-taugh MMA skills, he was asked to fight on a short notice for a local promotion. Still in his work uniform, Glenn left his work at a local Staples shift early in Marshalltown, rushing out to the venue, in time for a few stretches, and stepped in the cage 5 minutes later, winning his first fight. This win set of his MMA career where he put it “He was a tough guy, but I cut him up really good. I was shocked, I mean, I was fighting for my life in there. I was fighting grown men when I was in high school, and that first win meant everything.” After high school, Glenn moved to Cedar Rapids and attended a community college, majoring in physical therapy. He joined a MMA gym under Duke Roufus guidance where his training partner was Erik Kock and Ben Askren. Glenn fought 17 amateur fights in a short period with record of 15-1-1 and he would go on to fight 21 times professionally, losing only 3 bouts, and 97% of his wins have been by way of knockout, submission, or TKO prior signed by UFC. He moved to Milwaukee and left his employment at Costco to train full-time.
Glenn fought most of the fights in regional Midwest of American. He was the World Series of Fighting featherweight champion and Midwest Cage Fight featherweight champion. Glenn amassed a record of 18-3-1 prior signed by UFC. In his past 17 bouts, Glenn's only loss was to WSOF featherweight champion Lance Palmer, and he held notable victories over Johnny Case and Georgi Karakhanyan.
Glenn made his promotion debut on September 17, 2016 at against Evan Dunham in Texas. He moved up to lightweight for this fight bout replacing injured Abel Trujillo on 12 days notice. He was bested by Dunham via unanimous decision and this unsuccessful debut snapped a three-fight winning streak since losing his WSOF title to Lance Palmer in 2014. He next faced Phillipe Nover on February 11, 2017 at UFC 208. He outpointed Nover and win via split decision. Glenn faced Gavin Tucker on October 9, 2017 at UFC 215. He won the fight by unanimous decision. Tucker suffered four broken bones on his face during the one-sided beating from Glenn and many criticized the referee, Kyle Cardinal, for not stopping the fight. Glenn faced Myles Jury on December 30, 2017 at UFC 219. He lost the fight by unanimous decision. Glenn faced Dennis Bermudez on July 14, 2018 at UFC Fight Night 133. He won the fight via split decision. Glenn was scheduled to face Arnold Allen on November 30, 2018 at. However, Allen pulled out of the fight on November 16 citing a cut he received while training, and he was replaced by Kevin Aguilar. At the weigh-ins, Glenn weighed in at 148.5 pounds, 2.5 pounds over the featherweight non-title fight limit of 146. He was fined 20 percent of their purse, which went to his opponent Kevin Aguilar. The bout proceeded at catchweight. Glenn lost the fight via unanimous decision.
