* Dudley Moore as "Barnaby" - A recently-fired ad executive who starts a new career making insane, but effective, advertising campaigns.
* Daryl Hannah as "Sigourney" - A young, naive ad executive who initially finds Barnaby's antics off-putting, but comes to admire him.
* Robert Loggia as "C.D. 'Ducky' Doyle" - Barnaby's former boss and the head of the advertising agency.
* Paul Reiser as "Sam" - A rival ad executive who is jealous of Barnaby's success.
* Ellen Barkin as "Sally" - A high-powered ad executive who works with Barnaby.
* Anthony Perkins as "Dr. Rosen" - Barnaby's therapist.
* William Hickey as "The "Old Man" - A quirky, older ad executive who befriends Barnaby.
* John Mahoney as "Mr. Schwartze" - The owner of a toy company.
There are also several notable supporting actors. "Crazy People" is known for its star-studded cast!