The play opens on an outdoor scene of two bedraggled companions: the pensive Vladimir and the struggling Estragon who cannot remove his boots from his ailing feet, finally muttering "Nothing to be done." Vladimir takes up the thought,[nb 1] while Estragon vaguely remembers having been beaten the night before. Finally, his boots come off and the pair ramble and bicker pointlessly. When Estragon suddenly decides to leave, Vladimir reminds him that they must stay and wait for Godot—a segment of dialogue that repeats often. Unfortunately, the pair cannot agree on where or when to meet with this Godot.[nb 2] They only know that they are supposed to wait at a tree, and there is indeed a leafless one nearby.
Estragon soon dozes off and Vladimir rouses him but then stops him before he can share his dreams—another recurring motif. Estragon wants to hear an old joke, which Vladimir cannot finish, since a kidney ailment painfully urges him to urinate whenever he starts laughing. Estragon next suggests that they hang themselves, but they abandon the idea when the logistics seem ineffective. Estragon and Vladimir ponder the potential benefit of Godot's arrival but come to no definite conclusions. When Estragon declares his hunger, Vladimir provides a carrot (among a collection of turnips), at which Estragon idly gnaws, loudly reiterating their boredom.
"A terrible cry" heralds the entrance of Lucky, a silent, baggage-burdened slave with a rope tied around his neck, and Pozzo, his pompous and imperious master, who holds the other end and stops now to rest. Pozzo barks abusive orders at the slave, while acting civilly, though tersely, towards the other two, who are altogether dumbfounded. Pozzo eats chicken and wine without sharing any of it, before casting the bones to the ground. Estragon gleefully claims the bones, much to Vladimir's embarrassment, and Vladimir abruptly blows up at Pozzo for his mistreatment of Lucky. Pozzo ignores this and explains his intention to sell Lucky, who begins to cry. Pozzo presents a handkerchief for the pitying Estragon to wipe away Lucky's tears, but Lucky kicks Estragon in the shin. Pozzo then becomes maudlin and offers Vladimir and Estragon some compensation for their company. Estragon begins to beg for money when Pozzo instead suggests that Lucky can "dance" and "think" for their entertainment. Lucky's dance, "the Net", is clumsy and shuffling; Lucky's "thinking" is a long-winded and disjointed monologue—it is the first and only time that Lucky speaks.[nb 3] The soliloquy begins as a relatively coherent and academic lecture on theology but quickly dissolves into mindless verbosity, escalating in both volume and speed, that agonises the others until Vladimir finally pulls off Lucky's hat, stopping him in mid-sentence. Pozzo then has Lucky pack up his bags, and they leave at last.
Vladimir and Estragon, alone again, reflect on whether they have met Pozzo and Lucky before. A boy then arrives, purporting to be a messenger sent from Godot to tell the pair that Godot will not be coming that "evening but surely tomorrow." During Vladimir's interrogation of the boy, he asks if he came the day before, making it apparent that the two men have been waiting for an indefinite period and will likely continue. After the boy departs, the moon appears and the two men decide to leave to find shelter for the night, but they merely stand without moving.
It is daytime again and Vladimir begins singing a recursive round about the death of a dog, but twice forgets the lyrics as he sings.[nb 4] Again, Estragon claims to have been beaten last night, despite no apparent injury. Vladimir comments that the formerly bare tree now has leaves and tries to confirm his recollections of yesterday against Estragon's extremely vague, unreliable memory. Vladimir then triumphantly produces evidence of the previous day's events by showing Estragon the wound from when Lucky kicked him. Noticing Estragon's barefootedness, they also discover his forsaken boots nearby, which Estragon insists are not his, although they fit him perfectly. With no carrots left, Vladimir offers Estragon a turnip or a radish. He then sings Estragon to sleep with a lullaby before noticing further evidence to confirm his memory: Lucky's hat still lies on the ground. This leads to his involving Estragon in a frenetic hat-swapping scene. The two wait for Godot, as they did yesterday, and in the meantime distract themselves by playfully imitating Pozzo and Lucky, firing insults at each other and then making up, and attempting some fitness routines—all of which fail miserably and end quickly.
Pozzo and Lucky unexpectedly reappear, but the rope is much shorter than yesterday, and Lucky now guides Pozzo, rather than being controlled by him. As they arrive, Pozzo trips over Lucky and they together fall into a motionless heap. Estragon and Vladimir see an opportunity to exact revenge on Lucky for kicking Estragon earlier. The issue is debated lengthily until Pozzo shocks the pair by revealing that he is now blind and Lucky is now mute. He claims to have lost all notion of time, and assures the others that he cannot remember meeting them before, but also does not expect to recall today's events tomorrow. Pozzo's commanding arrogance from yesterday appears to have been replaced by humility and insight, though his demeanor is one of utter despair. His parting words—which Vladimir expands upon later—eloquently encapsulate the brevity of human existence: "They give birth astride of a grave, the light gleams an instant, then it's night once more." Estragon has again fallen asleep by the time Lucky and Pozzo depart.
While Estragon sleeps on, Vladimir is encountered by (apparently) the same boy from yesterday, though Vladimir wonders whether he might be the other boy's brother. This time, Vladimir begins consciously realising the circular nature of his experiences and existence: he even predicts exactly what the boy will say, involving the same speech about Godot not arriving today but surely tomorrow. Vladimir seems to reach a moment of revelation before furiously chasing the boy away, demanding that he be recognised the next time they meet. Estragon awakes and pulls his boots off again. He and Vladimir again consider hanging themselves, but they test the strength of Estragon's belt (hoping to use it as a noose) and it breaks; Estragon's trousers consequently fall down. They resolve tomorrow to bring a more suitable piece of rope and, if Godot fails to arrive, to commit suicide. Again, they decide to clear out for the night, though, once more, neither of them makes any attempt to move.