The 46-year-old American actor has previously played Bridget in two previous films, reported Daily Mirror.
It has been 11 years since Zellweger last starred as Bridget in the second film in the popular movie franchise, "Bridget Jones: The Edge of Reason".
Now, with filming for "Bridget Jones' Baby" underway in London, Zellweger is having trouble remembering how she mastered Bridget's English accent.
"Renee has been working on her accent with a voice coach and understands the importance of ensuring her accent is as good as it was in the previous two films," a source said.
Zellweger is reprising her role as Bridget in "Bridget Jones' Baby", due to be released next year. She is starring opposite Colin Firth, who is returning to the franchise as Mark Darcy, and newcomer Patrick Dempsey.