Scene i: After crossing the sea, Desdemona, Emelia, Cassio, and Iago arrive at Cyprus. As Cassio shows what a ladies man he is, Iago plots ways to use that against him. Iago often talks of webs and ensnaring Cassio and Othello. Cassio arrives and delivers the news of Othello's marriage and praises Desdemona highly. Desdemona arrives and waits for Othello's ship to come into port. It is at this time we meet Emelia, Iago's wife. When Iago insults her, Desdemona comes to her defense, but Iago only goes on to list the faults of women. Othello arrives and he and Desdemona reunite with passion and romance. Othello tells everyone the Turkish fleet has been defeated.

Iago persuades Roderigo that Desdemona is in love with Cassio in order to inspire jealousy, a major theme in this play. Iago gets Roderigo to agree to start a fight with Cassio while he is on the night watch that evening.

The act ends with Iago revealing his thoughts through a soliloquy. He admits he is attracted to Desdemona. He also reveals that he believes Othello slept with his wife, Emelia. Iago plans to make it even, "wife for wife." Iago also reveals that he believes Cassio has also slept with his wife.

Scene ii: Herald enters to deliver a proclamation.

Scene iii: Iago provokes Cassio to drink too much; he knows it is a weakness he has. If he is drunk, Iago plots, it will be easier for Roderigo to pick a fight. Cassio talks highly and romantically about Desdemona and Iago opposes him with sexually charged language and crude remarks.

Scene iii: Drinking and singing ensue. Iago talks Cassio into drinking more. Iago lies and tells Montano, the governor of Cyprus, that he is concerned about Cassio's drinking problem. Roderigo provokes Cassio into fighting. Montano intervenes and angers Cassio by calling him drunk. Cassio and Montano fight. Montano is wounded by Cassio. Iago tells Roderigo to go out and "cry mutiny." Othello comes in and stops the fight.

When Iago is questioned by Othello as to how the fight began, he acts as if he doesn't want to get Cassio into trouble. He sticks up for him until Othello gets angry and asks again. This time Iago tells him the truth, but reluctantly. Othello fires Cassio.

Everyone leaves except Iago and Cassio. Cassio is deeply ashamed and concerned about his reputation. Iago talks him into going to Desdemona for help because he believes Othello is so in love with her, he will do anything to please her. Cassio gratefully assents to the plan.

Iago goes into a soliloquy which reveals his evil capabilities. He refers to making "...the net, that will enmesh them all."

Roderigo comes back on the scene feeling ill-used. He is so dim witted that Iago talks him into staying in Cyprus; insisting that if he is patient, Desdemona would still be his. When Roderigo exits, Iago works out his plan again. He will get his wife to plead Cassio's case to Othello.