UFC officials confirmed the 185-pound contest on Tuesday, following an initial report by the Las Vegas Review-Journal.
Kennedy (18-4) is coming off a five-round unanimous decision over Michael Bisping in April. A former two-time Strikeforce title contender, Kennedy is 3-0 since joining the UFC roster last year with wins over Bisping, Rafael Natal and Roger Gracie.
A Cuban silver medalist in freestyle wrestling at the 2000 Olympic Games, Romero has posted stoppages in seven of his eight professional mixed martial arts wins.
Each middleweight will carry a four-fight win streak into the Sept. 27 contest.