Emma Woodhouse and her father attend the wedding of Miss Taylor, Emma's governess, and Mr Weston. Emma tells Mr Knightley, a family friend, that she played matchmaker to the couple. During a church service, she is inspired to pair Mr Elton, the vicar, with Harriet Smith, the illegitimate daughter of, she believes, a gentleman. Emma introduces herself to Harriet, who tells her about the Martins, a farming family, particularly mentioning Robert, the eldest son. Emma warns Harriet to be careful of her associates.

Harriet and Emma meet Mr Martin while walking, and Harriet is disappointed when Emma describes him as ungentlemanly, suggesting that Harriet turns her attention to Mr Elton. Later, Mr Elton watches Emma paint Harriet, and is complimentary about the subject. At the portrait's unveiling, he asks if he can arrange for it to be framed. Emma sees this as confirmation of his admiration of Harriet.

When Harriet tells Emma that she has had a proposal, Emma assumes that she means from Mr Elton. Once she learns that it is in fact Mr Martin, she advises Harriet to refuse him. When Mr Knightley discovers her interference, he scolds her for manipulating Harriet and damaging her chances of happiness.

At a Christmas party held by the Westons, Mr Weston mentions the absence of his son Frank Churchill, who he has not seen since his recent marriage. Frank has changed his surname to please his rich ailing aunt; as her heir, he complies with her demands for fear of being disinherited, despite the hurt to his father. Though Mr Knightley disapproves of Frank, Emma seems fascinated by him.

In the carriage home, Mr Elton asks Emma to marry him, much to her horror. She reminds him about Harriet, but soon realises that his admiration of the portrait was for the painter, not the subject. The next day, Emma tells Harriet what has occurred, and Harriet forgives her. They visit Miss Bates and discover that she is being visited by her niece, Jane Fairfax, a penniless but beautiful orphan (who Emma envies). The Bateses mention that during a visit to Weymouth, a Mr Dixon saved Jane from falling out of a boat.

Emma meets Frank for the first time a few days later, and he is charming and flirtatious. He drops hints that the married Mr Dixon is having an affair with Jane. When they later hear that Jane has received a piano from a secret admirer, Frank suggests that it is from Mr Dixon.

Mr Elton returns from holiday with his new wife. She tries to assist Jane in finding a governess position, but Jane seems to resent her help. Mr Knightley chides Emma for not showing Jane more kindness.

While Frank is away, Emma discovers that she doesn't miss him as she'd expected. On his return, a ball is held and he dances with Emma. Mr Knightley dances with Harriet after Mr Elton snubs her. The next day, Frank rescues Emma and Harriet from being accosted by beggars, inspiring Emma to see him as a potential partner for Harriet.

At a picnic, Frank teases Jane about Mr Dixon, and encourages Emma to be cruel to Miss Bates. Mr Knightley tells her off for being ungracious and mocking a woman who deserves better. She apologises to Miss Bates the following day.

Frank's Aunt dies, leaving him independent, and Mrs Weston informs Emma that he is engaged to Jane. Emma is not upset, and only feels resentful at being used by him to deceive everyone about his feelings for Jane. She tells Harriet about Frank's engagement, having earlier assumed her to be interested in him, but discovers that Harriet has feelings for Mr Knightley. Emma is jealous and realises that she has always loved him.

Later, when she sees Mr Knightley, they talk at cross-purposes, each assuming that the other loves someone else, until he confesses that he loves her. She goes to tell Harriet, but Harriet has become engaged to Mr Martin. Emma's father is upset at the news because he fears being lonely, but Mr Knightley agrees to move in with them both. At Mr Knightley's side at the harvest festival, Emma welcomes Harriet and Mr Martin.