Act V takes place in a chamber, where Cato is ruminating on his impending suicide. “Thus am I doubly arm’d: my death and life, / My bane and antidote, are both before me,” he says (54). Portius enters and attempts to stop Cato from killing himself, though he asks Cato to forgive him for that after Cato tells him to “learn obedience” and calls him “rash” (55). Cato tells Portius to check in on Cato’s friends as he takes a “moment’s sleep,” and Portius exits. He seems optimistic that Cato won’t kill himself, telling Marcia that “there’s hope / Our father will not cast away a life so needful to us all” (56).

Lucia admits that she “tremble[s]” when she thinks of the “stern and awful” Cato, but Marcia convinces her that her father is “all goodness” (57). Lucius enters, having just seen Cato sleeping peacefully, but Marcia worries that “his mind still labours with some dreadful thought” after Lucius reports that Cato said “Caesar, thou canst not hurt me” in his sleep (58).

Juba enters and announces that Caesar’s troops are approaching. Lucius advises they wake Cato, as Caesar is waiting to hear back from Cato before they approach.