The UFC 248 main event was largely a slow affair with very little output as both champion and challenger were very wary to engage, but it in the end, it was Adesanya’s kicking game that likely helped him to hold onto the middleweight title after five grueling rounds.
Adesanya improved to 19-0 after getting the better of Romero in Las Vegas on Saturday.
Judges scored the bout 48-47, 48-47 and 49-46 in Adesanya's favour.
After few exchanges between the fighters in the opening two rounds, Adesanya landed the more decisive blows thereafter.
Romero (13-5) has now lost four of his past five fights, including the previous three.
Earlier, Zhang Weili retained the women's strawweight title with a split-decision win against Joanna Jedrzejczyk in a classic.