Juliet is only thirteen at the beginning of Romeo and Juliet. Far more of the plot takes place around Juliet as she makes the change from immaturity to maturity. Juliet's parents and family members feature heavily in the plot and control most of her actions in the play. Juliet's youth is emphasised throughout the plot. This, despite her growing maturity, establishes her as a tragic heroine.

Juliet is presented as quiet and obedient in earlier scenes; however, she possesses an inner strength that enables her to have maturity beyond her years. When Lady Capulet suggests that she marry Paris, Juliet says that she will attempt to love him to make her happy.

Juliet is the dominant figure in her marriage with Romeo; she is the one who makes all of the plans for them to meet and solves the problem of her engagement to Paris. She is much more in control of her actions than Romeo, who seems to have most of his problems fixed for him. Juliet matures rapidly into this figure when she meets Romeo for the first time, changing from the innocent daughter to the heroine we see at the end of the play.

Juliet's love for Romeo changes her character completely. She becomes independent and defiant, disobeying her parents and the Nurse. In act 3, Lord Capulet demands his right as her father to marry her to Paris, threatening her with disinheritance and public shame. Juliet, however, is resolute in her decision to die rather than enter into a false marriage with Paris. At this point, when Juliet is most isolated from her family, even the Nurse betrays Juliet's trust by advising her to forget Romeo and comply with her father's wishes.

While Juliet is willing to give up her family name when she talks to Romeo on the balcony, her loyalty to her family doesn't change as the plot develops. She, like Romeo, is not concerned with the feud, but when Romeo is banished, she is hesitant to leave because of the death of Tybalt. She is clearly upset at the loss of her cousin and this is the first time we see her question her husband; "Shall I speak ill of him that is my husband?".

The moment when Juliet wakes up from the Friar's potion is one of the most tragic points of the play. We see her devastation at Romeo's suicide and in one of her only rash decisions, she stabs herself to join him in death.