Director Todd Phillips said Thursday Gibson's role was being recast because some of the actors and crew didn't want him involved in the project, which features Bradley Cooper, Neeson's "A-Team" co-star.
People.com said Neeson later confirmed he would play the part instead of Gibson.
"I just got a call to do a one-day shoot on 'Hangover 2' as a tattooist in Thailand, and that's all I know about it," Neeson told Daily Variety. "I just laughed my leg off when I saw 'The Hangover.' I was shooting in Berlin earlier this year and rented it on the hotel TV."