Garner began his professional mixed martial arts career in Florida. His career began with an arguably shaky start, compiling a 2–2 record over his first 18 months of competition. These fights included a KO victory over former Strikeforce and current UFC fighter Shawn Jordan and a TKO loss in the third round of his bout with Chris "Beast Boy" Barnett.

Garner soon joined M-1 Global and entered the 2010 M-1 Global Americas Heavyweight tournament. His opening fight was against Matt Hopkins, who had an 0–1 record at the time. Garner defeated Hopkins via TKO (Punches) in the first round. In the semi-final of the tournament, Garner faced Andrei Kapylou and defeated him via unanimous decision.

In the final of the Americas tournament, Garner faced Patrick Bennett. During the fight, Garner was able to neutralize Bennett's wrestling skills, by preventing every takedown attempt. Garner was able to catch Bennett with a hook, before unloading punches. Bennett attempted a single-leg takedown, but was thrown into the ropes. Garner was able to finish the fight via TKO at 2:31 of the opening round. Despite being a significant underdog in the M-1 tournament, Garner's win over Bennett made him the M-1 Americas Heavyweight Champion.

M-1 Global Western Europe Champion Guram Gugenishvili was scheduled to face the Eastern Europe champion, Maxim Grishin for the M-1 Global Heavyweight title. However, a month before the fight, Grishin withdrew with a knee injury providing Garner with an opportunity to challenge for the title. The fight took place at M-1 Challenge XXI: Guram vs. Garner. Garner was unsuccessful, losing via technical submission due to a guillotine choke.

Garner bounced back with two wins, one over Danny Lockhart and another over Pat Bennett in a rematch. He then faced Maxim Grishin for the Interim M-1 Global Heavyweight Championship, whom he defeated in the 5th round when Grishin submitted to punches. He later defended his title against Magomed Malikov, whom he KO'ed in the third round.

On June 21, 2012, Kenny would face Guram again, this time to unify his title with the M-1 Global Heavyweight Championship. Kenny would defeate Guram after the doctor stopped the fight in the third round and become the M-1 Global Heavyweight Champion. Kenny would then compete in the M-1 Heavyweight Tournament, but would lose in the opening round to Konstantine Gluhov via split decision.