In the days of Siddhartha, there were different ways of achieving the Enlightenment. Learning about the Enlightenment couldn't be taught with words, but can be taught mentally, and individually. Siddhartha went on a voyage to achieve enlightenment and finally learned about it. It all takes place in ancient India where he lived with his father who is a Brahmin.

Siddhartha was a handsome man who lived with his father in ancient India. Everyone in the village wants Siddhartha to become a Brahmin like his father. Govinda, who is Siddhartha's best friend, together they perform all the rituals of religion and does all the rituals which bring him peace and happiness. Siddhartha doesn't want to become like his father, he feels that his father and the elders of the village have not achieved enlightenment and he feels if he keeps living with his father, he will never learn. Siddhartha longs for something more, that the elders haven't done. Siddhartha and Govinda want answers for the achievement of the enlightenment.

One day, Samanas passed through the town begging for food. Samanas believed enlightenment can be reached through asceticism. Siddhartha believes that the Samanas can provide him with some answers. Siddhartha then joins the Samanas even though his father doesn't want him to join.

Govinda also wants to find a path to enlightenment, and he joins Siddhartha in his new life. Siddhartha adjusts quickly to the ways of the Samanas. The Samanas have been as unsuccessful as the Brahmins Siddhartha and Govinda left behind. Siddhartha and the other Samanas begin to hear about a new holy man named Gotama, the Buddha who has learned the total spiritual enlightenment called Nirvana. Siddhartha and Govinda inform the leader of the Samanas of their decision to leave and join with the Gotama's.

Siddhartha and Govinda find Gotama's camp of followers and are taken in. Siddhartha is happy with Gotama, and he and Govinda are instructed in the Eightfold Path, the four main points, and other aspects of Buddhism. While Govinda is convinced to join Gotama and his followers, Siddhartha still has doubts. He has noticed a contradiction in Gotama's teachings. Siddhartha decides to learn from the pleasures of the body and the material world. Siddhartha meets a friendly ferryman, very happy with his simple life.

Siddhartha crosses the ferryman's river and goes to a city. He meets a beautiful courtesan named Kamala. He thinks she would be the best one to teach him about love, but Kamala will not have him unless he proves he can fit into the material world. She convinces him to take up the path of the merchant. Siddhartha soon finds employment with a merchant named Kamaswami and begins to learn the trade. Kamala then becomes his lover and teaches him what she knows about love.

Years pass, and Siddhartha's business increases tremendously in digits. He then becomes a rich man. He gambles, drinks, and dances, and anything that can be bought in the material world is his for the taking. He understands that the material world is slowly killing him without providing him with the enlightenment for which he has been searching. One night, he resolves to leave it all behind and departs without notifying either Kamala or Kamaswami. One night, after drinking, Siddhartha saw a river planning to drown himself, but instead he ends up falling asleep on the riverbank.

Govinda walks by and see's Siddhartha sleeping but doesn't notice that it is him until he woke up in the morning. Govinda would watch over him which shows how caring he is for anyone. Siddhartha looks for the ferryman he saw years ago. The ferryman, Vasudeva, radiates an inner peace that Siddhartha wishes to attain.

Vasudeva says he himself has learned about this sense of peace through many years of studying the river. Siddhartha expresses a desire to likewise learn from the river and Vasudeva agrees to let Siddhartha live and work beside him. Siddhartha studies the river and begins to take from it a spiritual enlightenment unlike any he has ever known. While sitting by the river, he contemplates the unity of all life, and in the river's voice he hears the word Om. Siddhartha studies the river and Vasudeva teaches Siddhartha the many secrets the river has to tell.

Birth and death are all part of a timeless unity. Life and death, joy and sorrow, good and evil are all parts of the whole and are necessary to understand the meaning of life. By the time Siddhartha has learned all the river's lessons, Vasudeva announces that he is through with his life at the river. He retires into the forest, leaving Siddhartha to be the ferryman. The novel ends with Govinda returning to the river to seek enlightenment by meeting with a wise man who lives there. When Govinda arrives, he does not recognize that the wise man is Siddhartha himself.

Govinda is still a follower of Gotama but has yet to attain the kind of enlightenment that Siddhartha now radiates, and he asks Siddhartha to teach him what he knows. Siddhartha explains that neither he nor anyone can teach the wisdom to Govinda, because verbal explanations are limited and can never communicate the entirety of enlightenment. He asks Govinda to kiss him on the forehead, and when Govinda does, the vision of unity that Siddhartha has experienced is communicated instantly to Govinda. Govinda and Siddhartha have both finally achieved the enlightenment they set out to find in the days of their youth..