The narrative is based on the documentary "Jamie: Drag Queen at 16", which followed the story of British teenager Jamie Campbell, who defied teachers and attended his high school prom as his drag persona Fifi la True.
Grant will play the role of Hugo and his drag queen alter ego Loco Chanelle, who supports the teen on his journey. And according to director Jonathan Butterell, the "Love Actually" star has been preparing for the role by binge watching U.S. reality show "RuPaul's Drag Race".
"Richard's loving it. It's something he's never done before," the filmmaker told Britain's Daily Mail newspaper. "He has now watched, I think, a thousand million episodes of 'RuPaul's Drag Race' to learn how the kids are doing it, and also studying the story of the drag queens of the late '80s and '90s."
The director went on to laud the 58-year-old's performance in drag as "extraordinary," and joked, "By the time he's got heels and a wig on he's about 8 foot tall."
"Catastrophe" actress and writer Sharon Horgan will portray Jamie's teacher Miss Hedges in the film, while "Happy Valley" star Sarah Lancashire has signed up to play the teen's mother, Margaret.
Newcomer Max Harwood, 21, will play the role of Jamie, and the movie is expected to begin filming in Sheffield, England later this month.