The scene is set in Caesar's house during a night of thunder and lightning, and Caesar is commenting on the tumultuous weather and upon Calphurnia's having dreamed of his being murdered. He sends a servant to instruct his augurers, men designated to interpret signs and appease the gods, to perform a sacrifice. Calphurnia enters and implores Caesar not to leave home for the day. She describes the unnatural phenomena that have brought her to believe in the validity of omens. Caesar replies that no one can alter the plans of the gods and that he will go out. When Calphurnia says that the heavens proclaim the deaths of princes, not beggars, Caesar contends that the fear of death is senseless because men cannot avoid its inevitability.
The servant returns with information that the priests suggest Caesar stay at home today because they could not find a heart in the sacrificed beast. Caesar rejects their interpretation, but Calphurnia does finally persuade him to stay at home and have Antony tell the senators that he is sick. Decius then enters, and Caesar decides to send the message by him; Decius asks what reason he is to give to the senators for Caesar's failure to attend today's session, and Caesar says to tell them simply that he "will not come. / That is enough to satisfy the Senate." Privately, however, he admits to Decius that it is because of Calphurnia's dream in which many "smiling Romans" dipped their hands in blood flowing from a statue of him. Decius, resorting to the flattery to which he knows Caesar is susceptible, reinterprets the dream and says that Calphurnia's dream is symbolic of Caesar's blood reviving Rome; the smiling Romans are seeking distinctive vitality from the great Caesar. When Decius suggests that the senate will ridicule Caesar for being governed by his wife's dreams, Caesar expresses shame for having been swayed by Calphurnia's foolish fears. He declares that he will go to the Capitol.
Publius and the remaining conspirators — all except Cassius — enter, and Brutus reminds Caesar that it is after eight o'clock. Caesar heartily welcomes Antony, commenting on his habit of partying late into the night. Caesar then prepares to leave and requests that Trebonius "be near me" today to conduct some business. Trebonius consents, and in an aside states that he will be closer than Caesar's "best friends" would like for him to be. In another aside, Brutus grieves when he realizes that all of Caesar's apparent friends are not true friends.
