During filming, Robin Williams and the rest of the cast and crew worked closely with the Make-A-Wish Foundation to fulfill the fantasies of several children who were at the time undergoing cancer treatment. The children appeared with Williams in scenes at the pediatric ward.
Patch Adams said that whenever the film's production would get stressful, Robin Williams would improvise a comedy set to make the cast and crew laugh.
One of the film's producers, Mike Farrell, met Patch Adams when Adams served as an advisor to the TV series M*A*S*H (1972), in which Farrell played B.J. Hunnicutt, one of the Army doctors.
Filmed partially at the University of North Carolina. Robin Williams did stand up comedy for some classes that were in session while filming.
Robin Williams accepted the lead role because he was previously offered Jim Carrey's role of Fletcher Reede in director Tom Shadyac's previous film Liar Liar (1997). Williams declined that role and the film went on to become an enormous box office success. As a result he asked Shadyac if he could have a role in his next film which turned out to be this movie. Shadyac offered it to him and he immediately accepted.