The 55-year-old actor admitted on Thursday's episode of Watch What Happens Live that he turned down the sequel because he didn't like the movie's script.
"They did come to me a couple years ago," Grant revealed. "They had a lovely idea for a film."
"I'm particularly difficult and queeny when it comes to scripts, and I couldn't quite make the script work for me," he explained. "They then made it without me and I'm sure it's brilliant."
Grant played Daniel Cleaver in Bridget Jones's Diary (2001) and Bridget Jones: The Edge of Reason (2004). Co-stars Renee Zellweger and Colin Firth will return as Bridget Jones and Mark Darcy in the third film.
"I think they're going to go ahead and do it without Daniel," Grant had told Free Radio in 2014. "The book's excellent, by the way, but the script is completely different -- well, the script as I last saw it."
Grant was unable to recognize Zellweger in a partially-obscured photo on Watch What Happens Live. The 47-year-old actress faced plastic surgery rumors in 2014 after fans deemed her nearly unrecognizable at a red carpet event.
"Not that it's anyone's business, but I did not make a decision to alter my face and have surgery on my eyes," Zellweger wrote in an op-ed for The Huffington Post last week.
Bridget Jones's Baby opens in theaters Sept. 16. Grant will next star with Meryl Streep in Florence Foster Jenkins, which opens Friday.