It's The '80s. Swinging bachelors Peter (Tom Selleck), Jack (Ted Danson), and Michael (Steve Guttenberg) are close friends and roommates, sharing an apartment and a fondness for the ladies. One day, however, their lives are turned upside down by the arrival of baby Mary on their doorstep, the result of one of Jack's one-night stands. Jack himself is out of the country on a film shoot, so Peter and Michael have to deal with the situation on their own until he comes home. Hilarity Ensues as the men navigate the complicated waters of raising a baby who slowly steals their hearts, while dealing with a bewildering secondary plotline involving heroin dealers.

Directed by Leonard Nimoy and released by Touchstone Pictures, this comedy film is a remake of the 1985 French movie Three Men and a Cradle starring Roland Giraud, Michel Boujenah and André Dussollier. It premiered in 1987 and became the highest-grossing movie of that year in the US. It got a 1990 sequel, Three Men and a Little Lady, set a few years later. Mary's mother Sylvia (Nancy Travis), who joined the men's household at the conclusion of the first film, gets engaged to fellow British thespian Edward, and announces that she and Mary will be moving to England. This is unwelcome news to the men, not only because of their love for Mary but also because Peter is in love with Sylvia.

A third movie with the title Three Men and a Bride was announced but appears to be stuck in Development Hell. A remake for The Hallmark Channel, titled Three Wise Man and a Baby, premiered on November 19, 2022.

Three Men and a Baby provides examples of the following tropes:

• Aborted Arc: At the end of the first film, Peter appears to finally be engaged to his on-again-off-again paramour Rebecca. She does not appear in the sequel and their relationship is not addressed at all in order to make him and Sylvia the central romance. Peter mentions having been briefly married previously, but it's not said if this was to Rebecca or a prior relationship.
• All Girls Like Ponies: In the sequel, Edward attempts to show Sylvia that he'll be a good stepfather to Mary by promising the little girl a horse.
• Armour Piercing Response: When Sylvia calls Peter selfish as a result of him not liking her fiancée Edward, Peter responds with the following:
  Peter: I'm selfish? At least I didn't leave my baby on a doorstep when she was six months old!
  • Of course, this leads to Sylvia giving him a slap.
• Ascended Extra: Nancy Travis (Sylvia) has a far more substantial role in the sequel.
• Blonde, Brunette, Redhead: A twist on the trope. Dialogue indicates that when the three men go to parties together, one is only allowed to hit on blondes, one on brunettes, and the third on redheads, so they don't find themselves competing for the same woman.
• Bouquet Toss: Three Men and a Little Lady ends with Sylvia handing her bouquet to Mary for her to throw. Jack catches it, and the film fades to the credits on his shocked face.
• British Stuffiness: Edward (who is also an Evil Brit) and to a certain extent many of his friends and relatives. Sylvia's mother too.
• The Cavalry: Invoked by Peter in the sequel, when he flags down the boarding school director (whom he knows to be besotted with him) for a ride to the ceremony; on the phone with Michael, he remarks that "the cavalry just showed up."
• Double Standard: Rape, Female on Male: In the sequel, headmistress Miss Elspeth Lomax is led to believe by Edward that Peter is in love with her, so she (portrayed as a man-hungry imbecile) aggressively tries to have sex with him, at one point pulling Peter on top of her while shouting "Take me!" before he talks her down while trying to maintain the lie. As if that's not bad enough, at the time this was in theaters Disney was airing combination TV spots for two films in a single ad and one with The Rescuers Down Under had the "Take me!" line at the end, followed by Wilbur (John Candy) saying "That's a fabulous idea!".
• The Diaper Change: Clueless men watching a baby? Natch.
• Doorstop Baby: The whole plot is triggered by this.
• Even Evil Has Standards: The heroin dealers leave baby Mary alone, even when gagging her babysitter and ransacking the apartment. (All the same, they do leave a note threatening to take the baby away next time, so it is only a partial example).
• Explain, Explain... Oh, Crap!: After Jack leaves an answering machine message that he is expecting a package on Sunday and that two men will stop by to pick it up later in the week, Michael assumes Jack means Mary and thinks nothing of the package that his and his roommates' landlady, Mrs. Hathaway, drops off while he is looking after Mary and Peter is out shopping for food and diapers. When the two drug dealers stop by to collect the package, Peter and Michael assume they are there to pick up Mary, and after they leave, Peter sits down on the sofa and absorbs the silence... until he finds a package under the cushions:
  Peter: Michael! What is this?
  Michael: Package.
  Peter: [tensely] When did it get here?
  Michael: Sunday. Mrs... Hathaway... [realises he and Peter have just made a horrible mistake]
• Filler: Nearly every review, positive and negative, bemoaned the heroin subplot that seemed like it came from a different movie^note admittedly, it didn't; the heroin subplot is in the original French movie, too than the comedic, gentle stuff with Mary, and wished it were excised altogether. Indeed, the film dispenses of it with almost half an hour left in the movie.
• From the Mouths of Babes: The opening scenes of A Little Lady, where Mary is quite absorbent of the things said around her:
  "What a crock!"
  (to a waiter) "What's a penis?"
• Getting the Baby to Sleep: The three-part 50s era song used as a lullaby.
• Heart Is Where the Home Is: Inverted in the sequel. The love triangle has Peter and Englishman Edward fighting over Sylvia, who is an Englishwoman. Edward is a horrible jerk who wants to send the titular little lady (Mary) Off to Boarding School, so Sylvia chooses Peter, the American Nice Guy.
• Heartwarming Orphan: Mary's not an orphan — both of her parents are alive and well — but since she's raised by her dad's two best friends for the first half of the original film, the trope is somewhat invoked nonetheless.
• Imagine Spot: The three fathers imagining Mary as a teenager educated at an English boarding school.
• Ironic Echo Cut: In the beginning of A Little Lady:
  Mary: What a crock!
  Sylvia: Mary! Where did you hear that?
  Peter: [on the phone] What a crock! [hangs up and notices everyone staring at him] What?
• Non-Indicative Name: Two men show up at the apartment and want "the package". Peter and Michael think they've come to pick up the baby — they actually want a delivery of heroin.
• Off to Boarding School: In the sequel, the men discover that this is Edward's plan for Mary.
• Ooh, Me Accent's Slipping: Nancy Travis' English accent was often quite patchy and unconvincing.
• Personal Arcade: There is a "Harlem Globetrotters" pinball table in the guys' apartment.
• Piss-Take Rap: Possibly as iconic as the lullaby scene from the first film, the three men in the second film perform a rap of questionable quality, leading Sylvia's unimpressed mother to declare I Need a Freaking Drink.
• Platonic Co-Parenting: In the sequel Jack and Sylvia are raising Mary together (along with Peter and Michael), and while they jokingly flirt a few times, they both agree there's nothing between them anymore. Jack ends up being the one to encourage Peter to act on his feelings for Sylvia.
• Playboy Has a Daughter: The titular baby is the daughter of Jack, the biggest womanizer of the three dads. But taking in the baby (who is a seven-year-old girl in the sequel) forces them to give up their Confirmed Bachelor ways.
• Rule of Three: Note the titles.
• Shipper on Deck: In the sequel, one of the reasons Peter doesn't act on his feelings for Sylvia is because he assumes she and Jack will eventually get back together. Jack assures him that isn't going to happen and that he's perfectly happy for Peter and Sylvia to get together.
• Sink or Swim Fatherhood: The basic premise of the story and source of most of the gags. The titular men are thrown right into the depths of being a single parent, without any prior experience or someone to help them out:
  • First, Peter and Michael have to figure out how to handle the most basic things around Mary and how to arrange their lives around the fact they have a newborn under their care.
  • Eventually, when Jack, the biological father, shows up in their apartment after a few days, the duo already get a hang of things to a controllable degree. They gleefully dump all the duties on Jack as a sort of payback for going through hell taking care of his daughter.
• Speak Now or Forever Hold Your Peace: The priest at Sylvia's wedding to Edward asks the question several times and even mistakes one woman's hat for her raising her hand above her head. After several minutes of stalling Edward tells him to get on with it. After the ceremony is over and Edward's plans for Mary exposed we finally get The Reveal that the priest was actually Jack under heavy prosthetics. Naturally this means the "marriage" is completely void as Jack isn't authorised to perform the ceremony, which means Sylvia is free to immediately marry Peter instead.
• Time Skip: Despite the sequel being released just three years after the original, Mary is now five years old.
• Undercrank: Most of the film's opening sequence is filmed this way.
• Wedding Deadline: Peter has to bring the proof that Edward wants to send Mary to boarding school to the church before Sylvia marries him.
• With This Ring: In the sequel, Mary hides the wedding ring as part of the efforts to delay the "I do" sequence until Peter arrives.