Siddhartha centers on the lifelong search of Siddhartha, the young son of a Brahman, for enlightenment. As a boy, he is trained in the traditional rituals and meditations of the learned, but there is a restlessness in his soul. He cannot stop questioning and speculating, and he doubts whether any of his teachers is truly enlightened. Against his father’s wishes, he decides to join a group of Samanas, wandering ascetics, and his friend Govinda accompanies him. For three years, Siddhartha lives the ascetic life of self-denial. He cultivates a dislike of the sensual world and tries to empty himself of desires in order to reach the innermost core of his being. Eventually, however, he becomes dissatisfied, and guesses that the Samanas are no closer to enlightenment than the Brahmans who had taught him in his early youth.

Leaving the Samanas, Siddhartha and Govinda travel to see Gotama the Buddha, who has the reputation of being a wise man and supreme teacher. The young men are impressed by the Buddha’s quiet bearing and peaceful countenance, but Siddhartha, unlike Govinda, does not become his disciple. Siddhartha is skeptical of all teachings, convinced that enlightenment cannot be taught but can only be experienced by the individual for himself. He resolves to leave behind all doctrines and teachers. This decision is a major turning point for him, as he becomes more accepting of himself and more ready to appreciate the beauty of the sensory world. He is now alone, free of past ties, and ready to travel in whatever direction he chooses.

The second part of the novel relates Siddhartha’s gradual immersion in the world of sensual and material activities. Reaching a large town, he meets Kamala, a beautiful courtesan. She teaches him the art of love and finds him employment with a rich merchant named Kamaswami. Siddhartha prospers in business, and, as the years go by, he becomes rich and acquires a taste for luxurious living. At first, he had regarded business as a game and was unable to take seriously the small pleasures and desires of ordinary people. Gradually, however, he becomes deeply entangled in the life he has chosen. He becomes ruthlessly acquisitive, gambles recklessly, turns discontented, weary, and full of self-disgust. When he realizes that he can no longer hear the inner voice which once guided him, he concludes that life is worthless and decides to leave the town, never to return.

This journey marks another turning point in his life. In despair, Siddhartha wanders into a forest and comes upon a river. As he is about to drown himself, from somewhere within the deepest recesses of his being he hears once more the sacred sound “om,” the beginning and ending of all Brahman prayers. In that moment, he realizes his folly. He falls into a restorative sleep, and when he awakes he feels reborn. He meets an old ferryman, Vasudeva, who invites Siddhartha to stay and live with him. Siddhartha becomes a ferryman, and as time passes he finds peace of mind with the saintly old man.

Many years later, followers of the Buddha, on a pilgrimage to see their dying master, come to be ferried across the river. Among the pilgrims is Kamala, who has renounced her former life to become a benefactress of the monks. She is accompanied by a son she bore to Siddhartha, conceived on their final meeting. When Kamala is bitten by a snake and dies, the boy is left in Siddhartha’s care. The youth is restless and bad-tempered, however, and he cannot return Siddhartha’s love; eventually he runs away, and Siddhartha never sees him again. Through his possessive love for his son and its sad outcome, however, Siddhartha learns to have sympathy for the common folk; their simple passions no longer seem trivial to him. He also continues to grow in his knowledge of the unity of all things. He talks at length with Vasudeva, whose attentiveness, love, and serenity seem to Siddhartha like that of God. Together they listen to the river, in which Siddhartha discerns the whole stream of cosmic life, good and evil, joy and sorrow.

In the final episode, Siddhartha meets Govinda for the second time since they parted as young men. Govinda is still a seeker, and he asks Siddhartha to share some of his wisdom with him but finds Siddhartha’s words strange and difficult to understand. Siddhartha asks him to kiss his forehead, and as he does so, Govinda experiences a transforming illumination. He sees all the forms of the cosmos—animals, humans, gods—both the good and the bad, contained in Siddhartha’s smiling face, and he realizes, as Kamala in her dying moments had also nearly guessed, that there is no difference between Siddhartha and Gotama the Buddha.