Nerissa makes her first appearance in act 1, scene 2 of The Merchant of Venice, in a gossiping dialogue with Portia, her mistress. She is often described as Portia's lady-in-waiting, a position which would suggest that her employer is a queen or princess. While Portia is not of royal rank, her hand in marriage is sought by kings and princes, and her companion, Nerissa, is a lady rather than a servant. It was fairly common in the Renaissance for wealthy women to have paid "companions" who were of a similar rank to their own socially but without fortune. It is into this class that Nerissa falls.

It is this social status which allows Nerissa to marry Gratiano, who is the approximate social equal of Bassanio and acts as his unpaid companion. Nerissa is obviously very close to Portia and talks to her as her closest confidante, seeming to be almost her shadow when the two go in disguise together to Venice and play the same trick to obtain their rings from their fiancés. Nerissa and Gratiano are both portrayed as loquacious, forthright, and lighthearted and therefore seem a well-matched couple. It is Gratiano who speaks the last words in the play when he assures both characters and audience,

Well, while I live I'll fear no other thing
So sore as keeping safe Nerissa's ring.