Mrs. Doubtfire stars Robin Williams as Daniel Hillard (played by Robin Williams), a middle aged father of three and husband who's care free lifestyle and goofy way of thinking causes him to quit his job as a cartoon voice actor and causes his wife, Miranda (played by Sally Field) to demand a divorce after he brings a giant party home for his kids without his wife's consent.
After losing a custody battle for the kids, Daniel takes up a job at a TV station, gets a small apartment and only gets to see his kids once a week. He cannot let this pass and goes to his brother who is a makeup artist and asks to be transformed into an old woman so he can pose as a prospective Nanny for his family without his ex-wife knowing.
Daniel is able to pull it off smashingly and goes over as a success with his wife and his kids, all except his eldest daughter who is defiant when unable to be with her father, unknowing of course that he IS Mrs. Doubtfire. Later on, the kids discover that their father is Mrs. Doubtfire when they catch her peeing standing up.
Daniel is at work one day playing around on the set of one of the TV stations shows when he thinks no one is around. The network head watches quietly, then confronts Daniel about his talents. The network head and essentially Daniel's boss Mr. Lundy sets up a dinner meeting to discuss Daniel getting his own show due to his talents. A big break for Daniel. Unfortunately, Miranda's birthday dinner is scheduled the same night, at the same restaurant.
Daniel is forced to go to the bathroom at the restaurant every few minutes to change from Mrs. Doubtfire and leave his family (along with his ex-wife's new boyfriend, Stu) to change out and become Daniel again to have dinner with Mr. Lundy in the same restaurant. Eventually, the charade is caught by Lundy when Daniel sits at his table dressed as Mrs. Doubtfire. When explaining himself, Daniel sees that Stu is choking due to his evil plan involving an allergy to pepper. Daniel saves Stu as Mrs. Doubtfire and the mask comes off, revealing his identity to everyone, including Miranda.
In the end, Daniel still has limited custody of the kids, but gets his own show as Mrs. Doubtfire.