Duffee knocked Grove down with a rook hook, and referee Herb Dean looked as if he would stop it right then, but gave Grove a chance to defend himself. Duffee pounced with a hail of unanswered strikes from the top, and Dean stepped in to call a halt to the action.
Afterward, Duffee credited his new camp at American Kickboxing Academy for their team environment in assisting him in his comeback.
"I had a really, really rough camp," he said. "I had a lot of bad stuff going on and couldn't do this without them."
Duffee hadn't emerged victorious in a fight since UFC 102 in August 2009, when he knocked out Tim Hague in just seven seconds. Since then he had only fought twice, losing to Mike Russow and Alistair Overeem, respectively. He's now 7-2 overall.
Grove lost his third straight, falling to 11-6-1.
In the co-main event, Colleen Schneider TKO'd Cherie Buck at 2:29 of round two with punches and elbows.
Shlemenko is currently awaiting a Bellator middleweight title match with Hector Lombard, and he took the opportunity to let Lombard know he's thinking about him.
"Hector, I kill you," he said simply.
Ryan Healy def. Paul Kelly via unanimous decision
Pierre Daguzan def. Chaitanya Gavali via unanimous decision
Bharat Khandare def. Soro Ismael via submission (strikes), Rd. 1
Alexander Shlemenko def. Ikuhisa "Minowaman" Minowa via TKO, Rd. 1
Anup Kumar def. Dilanga Rathnaveera via submission (rear naked choke), Rd. 2
Ricky Ranjeet Singh def. Salika Senanayake via TKO, Rd. 1
Colleen Schneider def. Cherie Buck via TKO, Rd. 2
Todd Duffee def. Neil Grove via TKO, Rd. 1