Irony in The Cask of Amontillado

Poe’s use of both verbal and situational irony adds to the chillingly humorous and unsettling tone of the story. From the beginning, the audience knows that Montresor sought revenge against Fortunato. Thus all of his gestures of friendship must be read for their double meaning: Montresor’s conversation with Fortunato can be read as a series of veiled threats that foreshadow the harm Montresor brings to Fortunato.
Irony also establishes Montresor as an untrustworthy narrator as much of what he says explicitly states one thing while meaning another. Because much of the irony within the story is dramatic irony, the audience knows something that the characters, or at least Fortunato, do not.

The Cask of Amontillado 4
"True—true..."   (The Cask of Amontillado)

Poe uses dramatic irony to reinforce Montresor’s deceitful nature and provide some dark humor. The reader knows that Fortunato is not in danger of dying from a cold, but rather of being murdered by Montresor. Montresor’s consolation is just a ruse to lead Fortunato closer to his death.

"imposture..."   (The Cask of Amontillado)

Poe uses irony to characterize Montresor as hypocritical. While Montresor criticizes Fortunato for being deceitful, Montresor himself is being deceitful by luring Fortunato to his house under false pretenses to murder him.

"luckily..."   (The Cask of Amontillado)

Having learned that Montresor intends to take revenge upon Fortunato we know that this meeting is anything but lucky for Fortunato. Poe's use of situational irony here helps shape Montresor's character by showing the ease with which he misleads the victim of his revenge, whom he calls his friend.

"Fortunato..."   (The Cask of Amontillado)

Poe's choice for the antagonist's name indicates that he intended it to be ironic—a dominant element in the story—because as the victim he is certainly not fortunate, and his fortune, or money, doesn't assist him in any way.