Elle Woods is hopelessly in love with her boyfriend, Warner Huntington III, who will attend Harvard Law School the following year. She excitedly expects him to ask her to marry him, but he breaks up with her instead, saying that he has to be with someone more "serious" if he plans on a career in politics.
After Elle spends days holed up in her room, Elle's two best friends Margot and Serena take her to get her nails done. While waiting, she finds an article about Warner's older brother and his new fiancée, whom he met in law school.
Desperate to win Warner back, Elle takes the Law School Admission Test (and scores 179 on it, one point below the highest possible score), applies to Harvard, and although the board of admissions is bewildered at her application and video essay, they are impressed, and she is accepted.
Upon Elle's arrival, she is ridiculed because of her looks and naive behavior, and she discovers that Warner is engaged to another student, Vivian Kensington.
After Vivienne tricks Elle into attending a party in a Playboy Bunny costume where she retaliates by insulting her, Elle has a discussion with Warner and finally realizes he will never respect her.
Now determined to succeed on her own, Elle studies hard and impresses her professors and classmates in many occasions, proving herself enough for Vivian to consider her a threat, and wins an internship with Professor Callahan, as do Warner and Vivian.
They work with Callahan along with Emmett as an associate attorney, to defend Brooke Taylor-Windham, a famous fitness instructor accused of murdering her much older billionaire husband, Hayworth Windham. Brooke was once Elle's fitness instructor and a member of her sorority.
Elle believes Brooke is innocent, but Brooke's stepdaughter, Chutney and the household cabana boy say she is guilty and that they saw Brooke standing over Windham's dead body, covered in his blood, while Brooke testifies that she loved her husband and only found him after he had been shot to death.
Brooke refuses to provide Callahan an alibi, but when Elle visits her in jail, Brooke admits that she had liposuction on the day of the murder. Public knowledge of this fact would ruin Brooke's reputation as a fitness instructor, so Elle agrees to keep it secret and refuses to reveal the alibi to Callahan.
Impressed by her integrity, Vivian starts to befriend Elle, also admitting that Warner was put on Harvard's wait-list and only got in because his father pulled some strings.
Elle also becomes disillusioned with Warner when he suggests she reveal Brooke's alibi and break her friend's trust just to further her career.
After the trial, Warner tries to reconcile with Elle, but she rejects him, explaining that she needs a boyfriend who is less of a "bonehead" if she is to be a partner at a law firm by the time she is 30.
Two years later, Elle, who has graduated with high honors, is the class-elected speaker at the ceremony, and has been invited into one of Boston's best law firms; Vivian is now Elle's best friend and has called off her engagement with Warner who graduated without honors, no girlfriend and no job offers.
Paulette has married her delivery man and is expecting a baby girl to be named after Elle; and finally, Emmett has started his own practice, is now Elle's boyfriend, and will propose to her that night.