Zarathustra is a sage and a prophet who has a great love of humanity. Because of this love, he desires to leave the solitude of his mountain home to teach others the great truth he has discovered: the truth of the overman. Zarathustra first comes to a village where he makes his pronouncement that God is dead. He goes on to say that the overman is the true state of being for which mankind should strive. The people reject him as a madman, however, and Zarathustra realizes that his teachings must take a different route.
Zarathustra then finds disciples who are willing to listen to his teachings. He teaches them in private, grooming them to attain the state of overman so that they may eventually carry on his teaching to the rest of the world. Zarathustra teaches them the key points of his knowledge. To become the overman, one must have envy, be a warrior, and not take pity on the world. But, just as disciples of other religious leaders do not at first understand their master's teachings, Zarathustra's disciples do not understand what he is trying to teach them. With much sadness, Zarathustra leaves his disciples to return to his mountain of solitude, encouraging them to go out and spread the word of his teachings.
Zarathustra has a vision in his solitude and realizes that his disciples have distorted his teachings. Zarathustra knows he must return to them to set them on the right path, so he once again leaves his mountain home and the animals who are his companions and goes to find his disciples in the Blessed Isles. Here he discovers that the mistake his disciples have made is to try and blend his new teachings of the overman with the old teachings of Christianity. Such a folly will never work because Zarathustra's way is pure while the teachings of Christianity only hold men back from finding true communion with nature and with themselves.
Zarathustra then begins to attack those that would distort his teaching into something it is not. He fights with the priests who still believe in the dead God and he quarrels with the leaders of the academy who would replace God with other pursuits of knowledge. Such pursuits do not lead to the true state of humanity, Zarathustra teaches, and scholars who follow them are just as foolish as the religious zealots.
He then attacks the poets as those who are responsible for creating such heavenly worlds in which religion has come to dwell. Poetry used to inspire men to dream and to believe in heaven and an afterlife. In the wake of the overman, poetry has lost its power; therefore God has nowhere to live. Zarathustra soon realizes, however, that he himself is weighed down by a great enemy: pity for mankind. It is his own love for humanity that has now begun to impede his true ascent to the overman. He despairs because though he loves humanity, he knows he must abandon it to find his own true state of being.
Zarathustra begins another journey back to his mountain. Along the way, he realizes the true nature of divinity. In a bout of sickness, he realizes for himself that everything that has happened will happen again. He achieves a state of bliss and lives in his happy solitude for many years on his mountain.
After many years, however, he hears a cry of distress from the superior human being. The superior human has studied Zarathustra's teachings and now wants to find Zarathustra himself so that he can attain the same state of bliss and communion with nature that Zarathustra has found. Zarathustra realizes the superior being is actually a group of human beings that includes kings, a sorcerer, and other seekers of knowledge that have come to his cave to learn the true nature of being from him. Zarathustra mocks these men and they attempt to subvert his own teaching. They hold a festival for a donkey in which they name the donkey as a new divinity and worship it. Zarathustra comes to a new understanding; though these men may not be the superior beings for which he is looking, they have learned to mock the symbols of Christianity and the old teachings, thus finding for themselves a true happiness. As the book ends, Zarathustra leaves his mountain once again to take this ultimate knowledge to those that would be his true children.