The new live-action flick is being directed by Ray Griggs with The Last Samurai's Ted Field as a producer.
Griggs is working with Peter Jackson's visual effects company Weta on the new film and pre-production is scheduled to start this year in New Zealand, according to Variety.
The rest of the voice cast will be announced soon and Griggs spoke about his decision to cast Gervais as Mole.
He said: 'It's a natural fit to have an iconic British actor star in an iconic British tale. I had Ricky in mind for this role from the inception of this project.'
Deja Vu's Bill Marsilli has written the adaptation of the Kenneth Grahame story.