Jealousy 1: This first hint of jealousy is seen as Egeus claims to Theseus that Demetrius has stolen Hermia's obedience and love. He is slightly jealous of the new man in his daughter's life. This father/daughter jealousy is of course natural, but is taken to extremes is the play. It is also just one type of jealousy explored in the five acts.
Jealousy 2: Helena is deeply in love with Demetrius, who is in love with Hermia. Therefore, Helena is jealous of Hermia's beauty and she claims that she too is as beautiful. She wonders what Hermia has that she doesn't that makes men follow her everywhere. So, out of jealousy, Helena tells Demetrius that Hermia and Lysander plan to escape to the woods so that he will follow them and she will follow him.
Act II, Scenes 1-2: "Night, A wood near Athens" & "Another part of the wood"
Jealousy 3: Oberon and Titania bicker over many issues, including their supposed "other" loves and the possession of the little Indian boy. These arguments stem both from jealousy. The fairy without the Indian boy is jealous of the other and will go to any length to get him back.
Jealousy 4: Helena, again, is in bitter sentiment over her mistreatment from Demetrius. However, she is hurt not simply because he is rude and mean to her, but because she is jealous of Hermia. She tells the audience that she is thought as beautiful as Hermia all through Athens and cannot understand why Hermia gets the attention of her beloved Demetrius. This jealousy translates into her perpetual chase after Demetrius.
Act III, Scenes 1-2: "The same spot in the wood" & "Another part of the wood"
Jealousy 5: When Lysander tells Hermia that he abandoned her in the middle of the night for Helena, Hermia is enraged with jealousy. The words that come out of Lysander's mouth hit Hermia and injure her, building her jealousy of Helena instead of building her frustration with Lysander.
Jealousy 6: The fights between both Lysander and Demetrius and Hermia and Helena all have something to do with jealousy. Lysander and Demetrius are jealous of one another and both want Helena, where they used to want Hermia. And Hermia and Helena fight because Hermia is jealous of Helena as the reverse used to be true.
Act IV, Scenes 1-2: "The same portion of the wood" & "Athens, A room in Quince's house"
Jealousy 7: Oberon decides that the trick has gone far enough and will restore Titania to her normal self. Whether he is jealous of Bottom's position with her or not is unknown. But, he does see her in love with another creature and then decides that the magic must end.
Jealousy 8: Oberon also decides that everything will go back to normal with all creatures in the forest. He has possession of the Indian boy and that fact illustrates that he is no longer jealous of Titania. Therefore, with his jealousy gone, everything is fine to go back to normal in the woods.
Jealousy 9: When Theseus sees the four lovers sleeping peacefully together, he is shocked because he knows how much they all hate each other. He says that jealousy is not far from hatred. This statement from Theseus resonates throughout the play and is illustrated through the characters' behavior. When they are jealous, they act enraged and as if they hate each other.
Act V: "Athens, The great hall in the palace of Theseus"
Jealousy 10: Jealousy exists in another form with Bottom. He loves attention and loves to speak. Therefore, he is jealous of stage time and plans to take all of it that he can. He overacts, speaks too much, and dies an elongated stage-death, stealing scenes from everyone on stage.