Mirrors appear throughout the play. While other characters might interact with a mirror briefly—as Caesonia does on occasion—they become a focal point for Caligula alone. Caligula interacts with a mirror before he interacts with any humans. On his first appearance, Caligula catches sight of his reflection. His last interaction in the play—other than with his assassins—is also with a mirror.

While Caligula is usually in complete command of others, he always comes up short when he sees himself. For someone who is so set on pursuing the impossible, on achieving the level of godhood, it is a rude awakening to be faced with his own image, with all the imperfections and limitations that image might imply. The mirror forces him to confront the reality that he cannot control himself and his own destiny.

Mirrors afford Caligula the opportunity for self-reflection. Most of his conversations with other characters border on the absurd, but when confronted with a mirror, Caligula must wrestle with his own inner contradictions. Self-reflection leads him, on two occasions, to striking or smashing the mirror. At the end of Act I, he hits the mirror with a gong-hammer to efface his reflection. Only after does he feel in control of the situation once again.