The Paul Feig-directed comedy follows Sandra Bullock as an FBI agent and Melissa McCarthy as a Boston police officer, who team up to take down a Russian mobster.
© PA Images / Stuart Ramson/AP
© Rex Features / Startraks Photo/Rex Features
McDonald is to play a villain, reports Deadline.
Last month, the film added Arrested Development's Tony Hale to the cast as a man who is arrested by McCarthy after trying to secure the services of a prostitute.
The Heat is set for an April 2013 release in the US and UK.
McDonald is best known for playing various recurring characters, especially the little boy Stuart Larkin, in the Fox sketch comedy MADtv.
Watch a clip of Michael McDonald as Stuart below:
