The play starts with Caesar celebrating his victory over Pompey with a military parade through the streets of Rome. The people of Rome show great support for him and some fear that Caesar has gained too much power and will become a dictator. In the first scene of the play we find two tribunes, Flavius and Murellus, scolding two commoners for celebrating Caesar's victory and remove decorations from all Caesar's statues. Cassius, an ambitious Roman general, conspires to kill Caesar together with other politicians, such as Casca, Decius, Cinna, Metellus and Trebonius. Cassius tries to have Brutus join them as Brutus has a great following in the city of Rome. By forging letters to make him think that the people of Rome are angry at Caesar, he manages to convince Brutus to kill Caesar.

The conspirators kill Caesar in the Senate by stabbing him several times. After the murder, Brutus addresses the people of Rome to explain why he decided to kill Caesar. Even if he loved him, Brutus explains that if Caesar became king they would all have become slaves. He killed him because he loves Rome more than he loved Caesar. He asks if he has offended anybody by killing Caesar and nobody replies. Anthony enters with Caesar's body and Brutus explains that even if he didn't participate in the killing, Anthony will receive a place in the commonwealth.