The three girls are sisters Penny (Durbin), Joan, and Kay Craig. They live in a Swiss chalet with their mother Dorothy, Dorothy having been divorced from their father Judson for at least a decade. Dorothy still carries a torch for Judson, and she is left in tears when a newspaper reveals that Judson is engaged to be married to one Donna Lyons. The girls decide on the spot to sail for America and get their father, a wealthy businessman, to dump his girlfriend and get back with their mom. Through comic misunderstandings Kay gets a British lord, Michael Stuart (Milland) to try and lure Donna away from Judson, but Michael winds up falling for Kay.
Three Smart Girls was a huge hit that helped keep financially strapped Universal afloat. It featured Star Making Roles for both Durbin and Milland. Durbin soon became one of the biggest stars in Hollywood, featuring in a series of musicals for the next decade, while the success of this film boosted Milland from supporting player to leading man.
Durbin reprised her character in two sequels, Three Smart Girls Grow Up (1939) and Hers to Hold (1943). Not to be confused with Three Wise Girls, a completely unrelated 1932 film starring Jean Harlow.
- Blonde, Brunette, Redhead: As revealed by the color posters for this black-and-white film.
- Divorce Is Temporary:
- With the girls doing all the heavy lifting, as the mother is left behind in Switzerland and doesn't show up in New York until the very end.
- Sure, Dorothy and Judson haven't even seen each other for a decade. No biggie.
- Disappeared Dad: In-Universe. Judson Craig has so thoroughly forgotten his daughters in Europe that he doesn't even recognize their names when informed of their arrival.
- Fanservice: Was there any other reason for the three sisters to be dressed in tight shirts and hot pants while sailing on a lake in the opening scene?
- Gold Digger: Donna Lyons and her harpy of a mother are particularly shameless in their pursuit of Judson's money. When Michael Stuart pops up as an even richer target, Donna dumps Judson without hesitation. Count Arisztid is this at the end, eyeing Donna's fancy rings while the Lyonses are beside themselves at the thought of landing a count.
- Guess Who I'm Marrying?: Not played completely straight, as Judson hasn't seen his daughters in a decade and didn't even bother to tell them he was getting married. Played straight after the girls arrive, however, and discover Donna to be an awful gold-digging shrew.
- Having a Gay Old Time: "All you have to do is make love to a girl," says Kay to Michael when trying to get him to win Donna's affections.
- Impoverished Patrician: Count Arisztid, the Hungarian noble that Bill tries to set up with Donna, is completely broke.
- Irrelevant Act Opener: The film opens with Penny singing a song while the three girls sail around a lake in a boat. This has nothing to do with anything, but it did give Deanna Durbin a chance to sing.
- Kubrick Stare: Kay shoots quite the Death Glare at Donna as Donna plays piano and sings for the family.
- Last-Second Word Swap: After Donna's bitchy mother puts an end to the engagement, Judson ends the conversation by saying "And you're an old—buzzard!"
- Meet Cute: Penny is supposed to meet with a dissolute Bulgarian count, who is supposed to come on to Donna in order to break up her romance with Judson. She is to recognize the count via a magazine that he will be holding. The count drops the magazine, which is picked up by Michael. Penny thus mistakes Michael for the count and ropes him into her break-up scheme.
- The Musical: Sort of. It isn't quite a full-on musical, but it does have three Deanna Durbin songs that are completely extraneous to the plot.
- No Name Given: The first name of Donna Lyons's mother is never mentioned.
- Parent with New Paramour: And the Craig daughters are none too happy about it.
- Sexy Backless Outfit: Glamorous Donna wears one of these every time she goes out, apparently.
- Split-Screen Phone Call: A rather unusual variant. The camera shows Donna's and Judson's wedding rings. It zooms in for a closeup. The two circles are filled up by shots of Donna's mother and a reporter, as the former calls the latter to tell him about the impending wedding.
- Tempting Fate: "Youre as safe in this cab as in your mother's lap," says the cabbie, who crashes the cab immediately afterwards.
- Worst News Judgment Ever: The love life of Judson Craig seems to be a subject of endless fascination for the New York media. Just the possibility of an engagement with Donna inspires a front-page newspaper article which alerts the sisters. Then later the announcement of his wedding date spawns another front-page headline.