Belonging to the theater of the absurd, Waiting for Godot can be described as having both a grim and playful mood. The characters lead a drab, unchanging existence in barren surroundings, but their absurd conversations keep the mood from sinking into total gloom. While the audience certainly reacts to the play with a fair bit of unease, this is balanced out with steady instances of amusement. In addition, the comfort that Vladimir and Estragon find in each other's presence offers touching moments that also give the mood a certain lift.
Nevertheless, the characters' conversations do feel quite gloomy. The heavy, serious diction in their lines—especially Estragon's—reflects their pessimism. Repeating words and phrases like "nothing," "wait," "waiting," "I don't know," they express their restlessness and uncertainty over their conditions. They don't know where they are or what they're doing, and, although they discuss both of these questions at length, they rarely reach any firm conclusions. Moreover, most of the characters suffer from feeble memories, and so they tend to forget any of the conclusions they may have been on the verge of reaching.
The relationship between Vladimir and Estragon has a redeeming effect on the mood, but they still go through periods of tension and doubt. Every now and then they bicker, and they sometimes refuse to listen to what the other has to say. Early in the first act, Estragon says that "There are times when [he wonders] whether it wouldn't be better for [them] to part." At the end of the play, he brings this up again: "I sometimes wonder if we wouldn't have been better off alone, each one for himself." Both times, Vladimir is able to convince him that they would be worse off apart. Although it's possible to argue that the play ends on a grim note, as it closes with Estragon and Vladimir standing still, it's also possible to argue that it ends on a note of intimacy and hopefulness—after all, they remain by each other's sides.