In Verona, Sampson and Gregory (Capulet servants) complain that they will not put up with insults from the Montague family. Abram and Balthasar (Montague servants) appear and the four start quarreling. Benvolio (Lord Montague's nephew) appears and tries to break up the quarrel, but Tybalt (Lady Capulet's nephew) appears and picks a fight with Benvolio. At length, officers try to break up the fight, even while Lord Capulet and Lord Montague begin to fight one another. The Prince of Verona (Escalus) appears and stops the fighting, proclaiming sentences of death to any that renew the fighting. At Montague's house, he, his wife, and Benvolio discuss how melancholy Romeo (Montague's only son) has been lately. Benvolio vows to find out why. Speaking with Romeo, Benvolio finds Romeo is in love with a woman who has sworn to stay chaste (Rosaline). Benvolio suggests pursuing other women, but Romeo refuses. Separately, Paris (a kinsman of the Prince of Verona) talks to Lord Capulet about wooing his daughter Juliet for marriage. Capulet responds that she is too young (nearly 14 years old) and must wait two years to marry, and then only to the man whom she chooses. Still, Capulet invites Paris to a party in the evening. Capulet's servant is sent to invite guests, but he can't read the list so he entreats Romeo to do so. Upon hearing of the party, Benvolio convinces Romeo to attend and compare his unattainable love Rosaline to more beautiful women to get his mind off Rosaline. At Capulet's house, Lady Capulet speaks to Juliet about her feelings for marrying Paris while Juliet's Nurse listens on, telling stories of Juliet's childhood. Juliet, although hesitant, promises to be courteous. Masked, Romeo, Mercutio, and Benvolio head to the Capulet party. Romeo is still depressed, saying he dreamt a fearful dream of an untimely death that will result because of the evening's events, but Benvolio just makes fun of him. At Capulet's house, the Montagues attend the party (in masks), Romeo spies Juliet, and he falls in love with her. Tybalt sees Romeo and takes up arms, but Lord Capulet attempts to calm him, though Tybalt vows to revenge Romeo's intrusion the next day. Juliet, too, falls for Romeo, but falls into despair when her Nurse informs her Romeo is a Montague, as does Romeo when he learns Juliet is a Capulet.

While leaving the party, Romeo hides in the orchard while Mercutio and Benvolio call for him to come out of hiding and go home with them; yet he will not. After they leave, Romeo appears and speaks to Juliet under her window, saying "But soft! What light through yonder window breaks? It is the East, and Juliet is the sun!" By and by they swear their love to one another. Juliet tells Romeo she'll send a messenger to him the next day to learn the details of their wedding. Having stayed up all night, Romeo visits Friar Lawrence's cell and tells him of this new love for Juliet. Although Lawrence is critical at first, Romeo eventually convinces him to marry them. In the street, Benvolio tells Mercutio that Romeo did not come home that night, and that Tybalt has sent the Montagues a letter challenging Romeo to a duel. Romeo appears and they tease him for hiding from them. Juliet's nurse and servant Peter appear and Romeo tells her to tell Juliet to go to the Friar's cell that afternoon to be married. The Nurse returns to Juliet and, though she skirts around the message, she finally tells Juliet the wonderful news. Soon, at the Friar's cell, he marries Romeo and Juliet, and Romeo plans to visit Juliet's bedroom that evening.

At the street, Benvolio and Mercutio encounter Tybalt and Petruchio, leading to Tybalt and Mercutio fighting since Tybalt tries to pick a fight with Romeo, but he refuses. Romeo tries to break up the fight, but Tybalt slays Mercutio under Romeo's arm, then Tybalt flees. As Mercutio dies, he declares "A plague on both your houses," since he is only a friend of Romeo's and not his kinsmen. When Benvolio informs Romeo that Mercutio is dead, Romeo seeks out, fights, and slays Tybalt in revenge. Benvolio convinces Romeo to flee. The prince appears and Benvolio explains all to him, at which the Prince exiles Romeo for slaying Tybalt. At the Capulet's orchard, Juliet waits for Romeo when her Nurse appears and informs her of Mercutio and Tybalt's deaths, and Romeo's banishment. Juliet falls into despair, realizing she would rather Tybalt dead than Romeo, but also that a banished Romeo is virtually dead. At the Friar's cell, he informs Romeo of the Prince's edict of banishment, putting him into despair. Romeo states he would rather be dead than banished. The Nurse arrives and tells Romeo that Juliet is sad too, but forgives Romeo. Still, Romeo pulls a dagger and tries to kill himself, but the Friar stops him and tells him to stay the night with Juliet, then flee to Mantua. At Capulet's house, he and Paris set the wedding date for Paris and Juliet to be three days hence. In Juliet's bedroom, Romeo says a tearful goodbye to Juliet. After he leaves, Lady Capulet appears and, while discussing Tybalt's death, states she will send a henchman to mantua to kill Romeo (though she never does). She then informs Juliet of her impending marriage to Paris. Juliet tells her parents she will not marry, but Lord Capulet commands it will be so. The Nurse, too, tells Juliet she should marry Paris. In private, Juliet decides to no longer trust the nurse and vows to kill herself if the Friar cannot find a way to save her from marrying Paris.

At Friar Lawrence's cell, Paris informs the Friar of his upcoming wedding to Juliet. When Juliet arrives to see the Friar, Paris politely leaves. The Friar, hearing Juliet threaten suicide, tells her of a "distilled liquor" she can take to fake death. He explains the drug will keep her asleep and seemingly dead for 42 hours, during which she can be placed in the Capulet tomb. Then, when she wakes, Romeo can be there waiting for her to take her to Mantua. Friar Lawrence send Friar John to Mantua with an explanatory letter for Romeo. Juliet returns to her father and apologizes for refusing to marry, causing her dad to move the wedding up to the next morning (two days early). In her bedroom, Juliet sends her mother and nurse away, then, after much worrying over the future, she drinks the vial of medicine and sleeps. Later in the early morning, all feverishly prepare for the wedding and Capulet sends the Nurse to wake Juliet. The Nurse wails upon finding Juliet "dead", summoning the others to find her and mourn. The Friar instructs all to prepare Juliet for her funeral.

In Mantua, Romeo's servant Balthasar arrives and tells Romeo that Juliet is dead. Romeo vows to see Juliet in her tomb and poison himself there, buying the poison from a poor Apothecary who illegally sells it to Romeo only because he (the Apothecary) needs the money. At Lawrence's cell, Friar John reports he could not deliver the letter to Romeo since he (John) got stuck in a quarantined house while searching for Romeo. Friar Lawrence heads to the cemetery with a crowbar. At the tomb, Paris and his page arrive and Paris mourns Juliet's death. Paris hides when he hears Romeo and Balthasar approach. Romeo orders Balthasar to leave him alone, no matter what he hears. When Romeo opens the tomb, Paris steps out and tries to stop him by provoking him to fight. Romeo entreats Paris to simply walk away and not fight, but Paris forces Romeo to fight him, resulting in Romeo slaying Paris. In sorrow, Romeo lays Paris in the tomb, while Paris' page secretly leaves to call the watch. Romeo finds Juliet and mourns her death, then drinks his poison and dies. Outside the tomb, Friar Lawrence arrives and meets Balthasar who tells the Friar that Romeo has been in the tomb for one half hour. Lawrence enters the tomb and finds Romeo and Paris dead. Juliet then awakes and spots Romeo. The Friar, upon hearing noises outside flees, leaving Juliet with Romeo. Juliet tries to kill herself with Romeo's poison, but can find none, either in the vial or on Romeo's lips. In desperation, she stabs herself with Romeo's dagger. The watch arrives, having found Balthasar and the Friar. The Prince and Lord and Lady Capulet arrive and learn Paris, Romeo, and Juliet are dead (amazingly to them, Juliet seems to have been alive, and then newly dead again). Lord Montague arrives and reports that his wife has died from grief over Romeo's exile, then learns himself of Romeo's death. Capulet and Montague make peace and swear to never fight again. They vow to build solid gold statues of Romeo and Juliet and place them side by side so all can remember their plight.