The characters in Amphitryon by Plautus are a mixture of mortals and gods that have become intertwined in this story of mistaken identity and psuedo-infidelity.

Amphitryon, the play's title character, is a leader in the Theban army. When the play begins, he has recently returned victorious from war and is looking forward to visiting his home and his wife. When he does go home and finds that his wife has shared his bed with someone she claims was him, Amphitryon questions whether or not he has gone mad.

Sosia is Amphitryon's slave who accompanied the general in battle. He is a fearful man who teeters on the edge of an existential crisis after encountering Mercury, who has stolen his identity.

Alcmena is the patient, devoted, and faithful wife of Amphitryon. She has spent the night with Jupiter thinking that he was her husband. When confronted with the chaos and accusations that come with her actual husband's return, she is reasonably distraught and confused.

Jupiter, the king of the gods, has become enamored with Alcmena. He has disguised himself as Amphitryon so that he can make love to the Theban woman without her realizing who he is. He uses his power to make time stand still that night in order to maximize his time with Alcmena.

Mercury, the son of Jupiter, spends the play helping his father get away with his ruse. He also provides the audience with exposition by giving the prologue. When Sosia threatens to interrupt the love-making, Mercury intercepts him. Mercury disguises himself as Sosia, which provides a comical interaction as the real Sosia tries to make sense of what he is seeing.

Blepharo, the ship's pilot, is a minor character in the story. Amphitryon has Sosia bring him to his house in an attempt to clear up the confusion. Seeing two Amphitryons thoroughly confuses Blepharo. Blepharo is appalled at the situation he encounters and the abuse that he receives and leaves in disgust.

Bromia is Alcmena's maid and another minor character in the play. She is a nervous person who fears calamity at every turn. She relays the account of Alcmena calling down a thunderbolt and the birth of the twins. She helps put everything to right by soothing Amphitryon's worries, reassuring him of his wife's devotion, and explaining just what happened between Alcmena and Jupiter.