Bridget Jones is 32, single, engagingly imperfect, and worried about her weight. She works as a publicity assistant at a publishing company in London where her main focus is fantasizing about her boss, Daniel Cleaver.
At her parents' New Year party, Bridget is introduced to Mark Darcy, a childhood acquaintance and handsome barrister, the son of her parents' friends. Mark calls Bridget foolish and vulgar, and she thinks he is arrogant and rude. Overhearing Mark grumble to his mother about her attempt to set him up with "a verbally incontinent spinster who smokes like a chimney, drinks like a fish, and dresses like her mother", Bridget forms the New Year's resolution to turn her life around. She begins keeping a diary to chronicle her attempts to stop smoking, stop drinking, lose weight, and find her Mr. Right.
Bridget and Daniel begin to flirt heavily at work, ahead of an important book launch, at which Bridget bumps into Mark and his glamorous and haughty colleague Natasha. Bridget leaves with Daniel and they have dinner, despite Daniel's notorious reputation as a womaniser. Daniel tells Bridget that he and Mark were formerly friends but as Mark slept with his fiancée, they now hate each other. Bridget and Daniel start dating.
Bridget is invited to a family party, originally a "Tarts & Vicars" costume party, so she ties it into a mini-break weekend with Daniel. They spend the day before the party at a country inn where Mark and Natasha are also staying. The morning of the party, Daniel says he must return to London for work and leaves Bridget dressed as a Playboy bunny to endure the party alone. When she returns to London and drops in on Daniel, she discovers his American colleague, Lara, naked in his flat. Bridget cuts ties with him and immediately searches for a new career. She lands a new job in television, and when Daniel pleads with her to stay, she declares that she would "rather have a job wiping Saddam Hussein's arse".
Bridget attends a friend's long-standing dinner party, where she is the only unaccompanied person. Once again she crosses paths with Mark and Natasha. He privately confesses to Bridget that, despite her faults, he likes her "just as you are". Sometime later, he allows Bridget an exclusive TV interview in a landmark legal case which boosts her career and allows her to see him differently.
Bridget begins to develop feelings for Mark, and when she misguidedly and somewhat disastrously, attempts to cook her own birthday party dinner, he comes to her rescue. After a happy dinner celebration with Bridget's friends and Mark, a drunken Daniel arrives and temporarily monopolises Bridget's attention. Mark leaves but returns to challenge Daniel and they fight in the street, eventually smashing through a window of a Greek restaurant. The fight eventually ends, with Bridget chiding Mark and he leaving, and after a self-serving appeal from Daniel, she rejects him as well.
Bridget's mother, Pamela, has left Bridget's father Colin and begun an affair with perma-tanned shopping channel presenter Julian. When the affair ends, she returns to the Jones family home and off-handedly reveals that Mark and Daniel's falling-out resulted from Daniel (then Mark's best friend at Cambridge University) sleeping with Mark's wife which Mark walked in on, not the other way around.
At the Darcys' ruby wedding anniversary party the same day, Bridget confesses her feelings for Mark, only to learn that he and Natasha have accepted jobs in New York and are on the verge of an engagement, according to Mark's father. Bridget interrupts the toast with an emotionally moving speech that peters out as she realises the hopelessness of her position. Although her words affect Mark, he still flies to New York. Bridget's friends rally to repair her broken heart with a surprise trip to Paris, but as they are about to leave, Mark appears at Bridget's flat.
Just as they are about to kiss for the first time, Bridget rushes to her bedroom to change into sexier underwear. Mark notices her open diary, reads her earlier unflattering opinions of him, and leaves. Bridget realizes what's happened and runs outside after him in the snow in just her tigerskin-print underwear, a thin cardigan and trainers. There's no sign of him and, disheartened, she's about to return home when Mark emerges from a nearby shop.
Bridget apologises for what she wrote and tries to persuade him "it's just a diary". Mark reveals he only left to buy her a new one, which he gives her, "to make a fresh start", and they kiss in the snow-covered street.
