Michel Marnet (Boyer) is a French painter who is better known as a notorious playboy. Marnet boards a ship bound for America, where he will meet his fiancee. While on board he meets Terry McKay (Dunne), a former nightclub singer who is also going home to meet her fiance Ken, who owns a department store. They initially try to avoid each other out of fear of gossip, but eventually they fall in love. They agree to leave their respective partners and marry. Michel, who needs to get a real job, suggests they rendezvous atop the Empire State Building in six months. He starts selling paintings, she goes back to work as a singer, and six months later they arrive for their Empire State Building rendezvous—but Terry is hit by a car as she crosses the street in front of the building. She is left with crippled legs, bound to a wheelchair. Michel thinks that she ditched him, and doesn't even know where to contact her in America to find out what happened. So he goes on broken-hearted, while she decides not to contact him and elicit his pity. But fate will bring them together again.
Love Affair received a very famous Shot-for-Shot Remake in 1957, titled An Affair to Remember, starring Cary Grant and Deborah Kerr and also directed by Leo McCarey. Another remake, titled Love Affair and less faithful and successful, appeared in 1994, with Warren Beatty and Annette Bening.
- Arc Words: Arguably, "pink champagne", symbolizing the glamour of their former lives and what they are giving up for each other.
- At the Opera Tonight: Terry and Michel meet for the first time after their missed appointment at the opera. He is too upset to talk to her, and he doesn't find out about her medical condition because she's in an opera seat.
- The Casanova: Michel is internationally famous for it. He tells Terry that he is returning home from a romantic rendezvous with the sister of the woman he's engaged to.
- The Chanteuse: Terry's old job, which she goes back to after leaving Ken.
- Chick Flick: Romance, tragedy, a Ladykiller in Love, fancy mink coats, yep.
- Contrived Coincidence / Rule of Romantic: Could Michel and Terry randomly meet at the opera? Sure! Could Michel happen to find her address while looking in the phone book for someone else with a name that ends with "Mc"? Sure he could!
- Deadpan Snarker: Terry does this constantly to Michel during their first meeting. It appears to intrigue him, implying Terry's Not Like Other Girls since she's uninterested in his romantic escapades.
- Diabolus ex Machina: Look before you cross the street, dammit.
- Everyone Can See It: Terry briefly passes a little boy on the deck who reveals she and Michel have been the talk of the liner. Terry harshly denies she and Michel are romantically involved with each other but the boy is unconvinced. A few days later, she and Michel would have their Official Kiss.
- Fallen-on-Hard-Times Job: Michel, who has never held a real job, can't sell his paintings in America so he has to paint billboards while saving up money to marry Terry. Eventually, he does get his art career going.
- Gory Discretion Shot: Terry's accident is portrayed as Terry running off-screen and then a loud sound of a car breaking followed by people on the street shouting and running towards the sound's origin. All we see is the exit/entrance of the clothes' store Terry had just left.
- Gray Rain of Depression: Happening in New York as Michel finally has to admit defeat and go home from the Empire State Building at closing time.
- Honor Before Reason: Terry refuses to let Ken pay for her to get better and be able to walk again because she thinks Nickie wouldn't approve, she knows Nickie can't afford it, and she thinks it would be ungrateful of her to let Ken give her back her mobility and then go marry someone else.
- Kissing Discretion Shot: Terry and Michel's Official Kiss plays it straight as the camera shows them move closer and zooms in on their hands. Then tilts up to show the kiss.
- Ladykiller in Love: Notorious playboy Michel falls hard for Terry.
- Meet Cute: Michel, who wants to keep a low profile on the ocean liner, sneaks to an abandoned area of the ship to read his letter, but the ocean breeze pulls it through a porthole. He discovers that the porthole leads to Terry's room.
- Nice Guy:
- Michel. For a Millionaire Playboy who admitted he's cheated on his fiancee with her sister and Really Gets Around enough to be considered breaking news on the radio, he is sincere, selfless, kind and a gentleman, making it obvious why he's a Chick Magnet.
- Terry, a typical staple for Irene Dunne's characters, may be witty but never cruel. Michel decides to confide his woes to her because, in his words, she has an honest face.
- Out-of-Context Eavesdropping: A cop is suspicious when he hears Michel's agent tell Michel that he sold one of Michel's paintings.Agent: I sold one! The woman! I got $100 for her!
- Orphanage of Love: After she's crippled, Terry gets another job as a singing teacher to the kids at an orphanage. It is plainly an Orphanage of Love, what with the headmaster being devoted enough to the children to hire Terry in the first place.
- Romantic False Lead: Ken comes back into Terry's life after her accident, but it's perfectly clear she won't end up with him.
- Tears of Joy: Both Terry and Michel get this in the final minute of the movie.
- Twerp Sweating: A variation, yet subverted and inverted. Terry and Michel's grandmother get along well and bond over their relationships with Michel. When Michel returns, the two women are laughing and explain they'd just compared how Michel acts when he doesn't get his own way, which makes them laugh again as Michel acts self-conscious, making them laugh harder.
- Worst News Judgment Ever: Michel's love life and his comings and goings are front-page headlines.