Hardy knocked out Tebaris Gordon with a flurry of punches after just 17 seconds as part of the "Dana White Tuesday Night Contender Series" in Las Vegas.
Hardy improves to 2-0 after handing Gordon (3-1) his first loss. All five of his fights since leaving the NFL, including three amateur fights, have ended in knockouts by Hardy.
At least one participant in the show is offered a multi-fight deal by UFC at the end of each episode.
Hardy was awarded a UFC developmental contract by White after recording a 57-second knockout win over fellow ex-NFL player Austen Lane in his professional debut on the show in June.
Terms of Hardy's contract aren't available.
Hardy made the Pro Bowl and was second-team All-Pro as a member of the Panthers in 2013. The 29-year-old was arrested in 2014 after allegedly assaulting his ex-girlfriend and pleaded guilty to a misdemeanor drug charge in 2016.
--Field Level Media