The film received positive reviews and was a box office success. This film is number 43 on Bravo's "100 Funniest Movies".
Bob Wiley is a good-natured man with great work ethic, but he suffers from multiple phobias and is divorced because his ex-wife likes Neil Diamond. He feels good about the results of an initial session with Dr. Leo Marvin, an egotistical New York psychoanalytical psychiatrist. However, Bob is immediately left on his own with a copy of Leo's new book, Baby Steps, when the doctor goes on vacation to Lake Winnipesaukee, New Hampshire for a month. Unable to cope, Bob follows Leo to his vacation home. Leo is annoyed because he does not see patients on vacation, but seeing how desperate Bob is tells him to "take a vacation" from his problems. Bob seems to have made a break through, but the next morning, he tells Leo that he decided to take a vacation in spirit and fact in Lake Winnipesaukee as a guest of the Guttmans, a couple who own a coffee shop and happily welcome Bob as their guest. The couple encourages Bob to be around Leo, as they hold a grudge against Dr. Marvin for purchasing the lakeside home they had been saving for years to buy.
Bob suggests that they start a friendship, but Leo thinks being friends with a patient is beneath him and attempts to avoid any further contact. However, Bob swiftly ingratiates himself with Leo's family, who think Bob may have some foibles, but is otherwise a balanced and sociable man. Leo's children, Anna and Sigmund, find that Bob relates well to their problems, in contrast with their father's clinical approach. Bob gains an enjoyment of life from his association with them; he goes sailing with Anna and helps Sigmund to dive into the lake, which Leo was unable to help him with. Leo then angrily pushes Bob into the lake, and Leo's wife, Fay, insists on inviting Bob to dinner to apologize. Bob, who believes Leo's slights against him are accidental and/or part of his therapy, accepts the invitation. After dinner, a thunderstorm forces Bob to spend the night. Leo wants Bob out of the house early the next morning before Good Morning America arrives to interview him about Baby Steps. The television crew arrives early and, oblivious to Leo's discomfort, suggest having Bob on the show as well. Leo is tense and makes a fool out of himself during the interview while Bob is relaxed and speaks glowingly of Leo and the book, unintentionally stealing the spotlight.
Outraged, Leo throws a tantrum and then attempts to have Bob committed, but Bob is soon released after telling the staff of the institution therapy jokes, easily demonstrating his sanity. Forced to retrieve him, Leo then abandons Bob in the middle of nowhere, but Bob quickly gets a ride back to Leo's house while various mishaps delay Leo until nightfall. Leo is then surprised by the birthday party that Fay has been secretly planning for him, and he is delighted to see his beloved sister Lily. But when Bob appears and puts his arm around Lily, Leo becomes enraged and attacks him. Bob remains oblivious to Leo’s hostility until Fay explains that Leo has a grudge against Bob, who then agrees to leave. Meanwhile, Leo breaks into a general store, stealing a shotgun and 20 pounds of explosives. Bob is kidnapped at gunpoint by Leo, who leads him deep into the woods, ties him up, and straps the explosives onto him, calling it "death therapy". Leo then returns to the house, gleefully preparing his cover story. Believing the explosives to be props and used as a metaphor for his problems, Bob applies Leo's "Baby Steps" approach and manages to free himself both of his physical restraints and his fears; he reunites with the Marvins and praises Leo for curing him with "death therapy". The Marvins' vacation home detonates after Bob reveals that he left the black powder inside. The shock leaves Leo in a catatonic state.
Some time later, the still-catatonic Leo is brought to Bob and Lily's wedding. Upon their pronouncement as husband and wife, Leo regains his senses and screams, "No!" but the sentiment is lost in the family's excitement at his recovery. Text at the end reveals that Bob went back to school and became a psychologist, then wrote a best selling book titled Death Therapy, and that Leo is suing him for the rights.
Before Frank Oz was hired to direct, Garry Marshall was considered, and Woody Allen was approached to play Dr. Leo Marvin. Allen was also considered to direct and possibly co-write the script with Tom Schulman. However, because Allen had always generated his own projects rather than getting handed an existing property to make his own, Oz was officially hired to direct. Allen also declined the role, thus Richard Dreyfuss was ultimately cast. Patrick Stewart was also considered for the role. Early in development, Robin Williams was attached to the project.
Oz admitted in interviews that there was tension on the set during the making of the film. In addition, both Murray and Dreyfuss have confirmed in separate interviews that they did not get along with each other in real life:
It’s entertaining—everybody knows somebody like that Bob guy. (Richard Dreyfuss and I) didn’t get along on the movie particularly, but it worked for the movie. I mean, I drove him nuts, and he encouraged me to drive him nuts.
How about it? Funny movie. Terribly unpleasant experience. We didn’t get along, me and Bill Murray. But I’ve got to give it to him: I don’t like him, but he makes me laugh even now. I’m also jealous that he’s a better golfer than I am. It’s a funny movie. No one ever comes up to you and says, “I identify with the patient.” They always say, “I have patients like that. I identify with your character.” No one ever says that they’re willing to identify with the other character.
Producer Laura Ziskin recalled having a disagreement with Murray which led to her getting tossed into a lake by him. Ziskin confirmed in 2003, "Bill also threatened to throw me across the parking lot and then broke my sunglasses and threw them across the parking lot. I was furious and outraged at the time, but having produced a dozen movies, I can safely say it is not common behavior."
The movie was filmed in and around the town of Moneta, Virginia, located on Smith Mountain Lake. Production had to move south because at the real Lake Winnipesaukee in New Hampshire, the leaves were already turning for the fall season. While there is a lake in New Hampshire named Winnipesaukee, there is no town by that name (as the film implies). Filming lasted from August 27 to November 21, 1990.
For the scene in which Bob accidentally blows the house up, producers used a 3/4-sized model replica of the actual house that they detonated on a nearby lot.
The scenes of Bob arriving in town on the bus with his goldfish were filmed in downtown Moneta, which was spruced-up and repainted for the movie. The local institute which Leo tries to commit Bob in is actually the local Elks National Home for retirees in the nearby town of Bedford, Virginia.
Scenes were also shot in New York City. According to Oz, Murray "was really frightened about shooting in the city."
Murray confirmed that he improvised a lot in this movie.
What About Bob? was a financial success. It grossed $63 million domestically during its original theatrical run plus an additional $29 million in video rentals and sales bringing its overall domestic gross to $92 million.
Critical reaction was also favorable. Review aggregation website Rotten Tomatoes gives the film a score of 83% based on reviews from 40 critics with the consensus: "Bill Murray and Richard Dreyfuss' chemistry helps make the most of a familiar yet durable premise, elevating What About Bob? into the upper ranks of '90s comedies."
Leonard Maltin also gave the film a favorable review: in Leonard Maltin's Movie and Video Guide he gives the film three stars out of a possible four, saying it's "a very funny outing with Murray and Dreyfuss approaching the relationship of the road runner and the coyote." Maltin faulted the film only for its ending, which he found very abrupt and silly.
However, the film received criticism from The Baltimore Sun film critic Lou Cedrone: "It is too predictable and deals with a situation that is more irritating than amusing."
In April 2015, it was reported that Richard Dreyfuss sued The Walt Disney Company over the film's profits. Dreyfuss has claimed that Disney refused to hire his chosen auditor, Robinson and Co. Christine Turner Wagner, widow of Turner & Hooch (1989) producer Raymond Wagner, is also involved with the lawsuit.
A television pilot adapted from the film and featuring two female leads was ordered by NBC in 2017. The show, called What About Barb? cast Jessica Gunning as the titular character and Leah Remini as the psychotherapist.