As a play about conspiracies, political intrigue, and secret plots, Julius Caesar is ripe with examples of deception. For instance, in act 2, scene 2, Decius lies directly to Caesar to get him to come to the Senate, intentionally misinterpreting Calpurnia's nightmare and telling Caesar that the senators plan to give him a crown. This deception leads Caesar to abandon his caution, which results in his assassination.
Earlier, in act 1, scene 2, Cassius wants to get Brutus involved in the assassination plot. Brutus is popular with the Roman people and therefore would be an important addition to the conspiracy. In their conversation at the games, Cassius deceives Brutus by exaggerating the support that he has among the patricians. He does this by feeding Brutus's ego and vanity and telling him that he is the most popular Roman after Caesar.
The greatest deception in this play is probably Marc Antony's funeral oration. Antony shrewdly lets the conspirators believe that they can control him. He allows them to think that he is powerless without Caesar's support and will fall into line with the new regime. However, Antony uses his speech at Caesar's funeral to whip the crowd into a frenzy and turn them against the conspirators.