Elle's snobby classmates disapprove of her attire, and the only person who is willing to help her out is the law technical assistant, Emmett Forrest ("The Harvard Variations"). However, he can not protect her in class with the blood-thirsty Professor Callahan ("Blood in the Water"). Elle, being under-prepared, gets kicked out of class by Vivienne Kensington, who happens to be Warner's new girlfriend. This tragedy summons the apparitions of the sisters of Delta Nu, who, acting as a greek chorus visible and audible only to Elle, tell her to be positive ("Positive"). Elle, deciding that being blonde is a problem, heads to the salon The Hair Affair, where she meets beautician Paulette who tells Elle that when she is down, she puts on her favorite CD, and dreams of Ireland ("Ireland"). At the Hair Affair, Vivienne gives Elle a surprise invitation to a "costume party". Paulette sends Elle off with a costume for the party, her positivity and blonde hair still intact ("Ireland Reprise").

Walking into the party as a Playboy bunny, Elle realizes that she has been tricked by Vivienne into thinking it was a costume party, but, with courage, Elle seeks out Warner in an effort to win him back ("Serious Reprise"). Warner still does not take Elle seriously. Elle runs away from the party, only to run into Emmett. Emmett is un-moved by Elle's love problems, due to the fact that he has had a difficult, self-run life. He tells her that she has to buckle down and study. He slowly gets Elle to re-examine her priorities until she defeats Warner in a classroom discussion ("Chip on My Shoulder"). Warner and Vivienne win two of Callahan's coveted internship positions, and Warner proposes on the spot in front of Elle. Before Elle's heart can break, Emmett shows her the internship list. Below the names of Vivienne, Warner, and Enid is the name "Elle Woods" ("So Much Better").

Act II

Callahan, Emmett, and the four interns are studying the jump rope workout video of their newest client, fitness mogul Brooke Wyndham ("Whipped into Shape"). Brooke's step-daughter, Chutney, is accusing Brooke of murdering Brooke's much older husband. Callahan and the interns visit Brooke in jail, but are unable to extract an alibi from her, until she is alone with Elle. Elle recognizes Brooke as a former Delta Nu member. Swearing Elle to secrecy, Brooke reveals her alibi: she was getting liposuction on the day of the murder. Not willing to betray her Delta Nu trust, she asks Callahan to trust her when she says that she is innocent. Callahan then releases his rage on Emmett. Emmett begs Elle to break her promise. Elle refuses, but then offers to help impress Callahan in a different way by taking Emmet to a department store ("Take It Like a Man"). The results impress both of them.

Back at the Hair Affair, Elle is getting a manicure when in walks the sexy new UPS man, Kyle. Paulette is nothing short of stunned, but she is too shy to talk to him, believing that she has nothing to offer. As she bends down to pick up the package, however, Margot, Serena and Pilar are summoned by Paulette's amazing 'bend and snap', now visible not only to Elle but also to Paulette ("Bend and Snap"). The sorority girls tell Paulette to use the bend and snap on Kyle, but when she does, after his return to look for his stylus, she accidentally breaks his nose.

On the third day of Brooke's trial, Brooke's pool boy, Nikos Architacos, shocks the court by claiming to have an affair with Brooke. Brooke denies it, and Elle believes her. Elle tries the bend and snap, twice, in front of Nikos and gets no response. Elle concludes that he is gay ("There! Right There!"). Callahan, however, believes him to be simply European. It is revealed by Carlos, Nikos' boyfriend, that Nikos is gay and European.

Later that night in Callahan's office, the interns celebrate Elle's skill. However, after dismissing Emmett and the other interns, Callahan kisses Elle, earning himself a slap. It is then revealed that Callahan only hired Elle to be 'blonde arm candy', and he fires her. As a heartbroken Elle is left stunned in the office, Warner and Vivienne, who both saw the kiss, though Vivienne pushed Warner out of the way before he could see the slap, enter. Warner believes Elle is sleeping her way to the top and makes a joke on her expense, upon which Vivienne tells him to shut up and they both leave. Elle gives up on law school and love and prepares to go home against Emmett's asking her to stay ("Legally Blonde").

Elle heads to the Hair Affair to say good-bye to Paulette, but before she can leave, Vivienne shows up and convinces Elle otherwise ("Legally Blonde Reprise"). Confident again, she puts on a pink (her signature color) dress and leads a parade back to the courtroom, picking up her parents, Margot, Serena and Pilar, who randomly show up to watch her in person, on the way. The last person they pick up is Kyle, who takes a liking to Paulette. Back at the trial, Brooke fires Callahan and hires Elle. Emmett, being a licensed lawyer, supervises Elle. Chutney goes to the witness stand and her testimony is damning, but Elle triumphs by revealing Chutney's lie with her knowledge of hair maintenance ("Omigod You Guys Reprise"). Chutney accidentally confesses that she was the one who killed her father, believing him to be Brooke, because she hated having a mother younger than herself. Elle's victory is so great, that Warner proposes to her, having been dumped by Vivienne. Elle kindly refuses, claiming to have been changed ("Find My Way").

Three years later, Elle ends up as the valedictorian of her class. Paulette tells the audience that Enid practices family law, Vivienne's training for the peace corps, and Warner quits law school to pursue a modeling career. Callahan ran for governor but was defeated, of course, and his wife hired Emmett to handle their messy divorce. Paulette married Kyle, had two kids, and is pregnant with a third. At the end of the graduation ceremony, Elle proposes to Emmett, and Emmett accepts.