The third film in the beloved franchise centers on the titular character's life as she navigates a pregnancy, two possible fathers, and an unsure future.
One of those men is a familiar face: Mark Darcy (Colin Firth), who in the first two films battled playboy Daniel Cleaver (Hugh Grant) for Bridget's heart -- and won.
In this installment, Mark and Bridget are on the outs and Bridget wins the affection of Jack (Patrick Dempsey), a rich entrepreneur who unlike Cleaver doesn't really have an obvious downside.
"The nice thing about playing this role is that I didn't have to choose," Zellweger told CNN during the cast's promotional tour. "I could argue on behalf of either of these guys."
If you ask Firth, though, Bridget's choice is a simple one.
"She's a lot better off with the other guy," Firth said. "I've been nothing but a disappointment all of these years."
Zellweger, whose role marks a return to movies after a six-year break, laughed at Firth's assessment.
"That was brilliant. Did you see what he did? He played the empathy card," she said.
Dempsey, who made a high profile exit from "Grey's Anatomy" last year, sees Jack's addition as an opportunity.
"I think going into the unknown with Jack is a good thing," he said. "It's a clean slate -- which is good and bad."
Whatever Bridget's decision, Zellweger said, the drama is the franchise's gain.
"It's an interesting new dynamic," she said. "It's a more sophisticated type of competition because they're both great guys."
"Bridget Jones' Baby" opens September 16.
CNN's Neil Curry contributed to this report from London.