Tolstoy divides Childhood, Boyhood, Youth into three parts: childhood, boyhood, and youth. Each part is narrated by the main character, Nikolai, and tells the story of his early years from his upbringing on his family estate to his university education in Moscow.

Nikolai portrays himself as a shy, sensitive child who is constantly trying to improve himself. The first chapter of this book is set on the family estate where Nikolai lives with his parents, his brother and sister, family servants (including a tutor(, and serfs. This section doesn't have much of a story. It mostly describes scenes in Nikolai's childhood and the relationships he has with people such as his father, whom he describes as

A man of the past age, and had the indefinable character common among those who were young then: a compound of chivalry, enterprise, self-confidence, amiability, and licentiousness.

At the end of the first chapter, Nikolai experiences the first major and tragic event of his life when his mother dies in "great agony."

Nikolai moves into boyhood with "painful memories" but a better understanding of the world. This is characterized by the opening chapter, where he leaves his estate for Moscow and on the way sees the poverty of villagers and beggars and begins to comprehend the difference between the wealth of his family and the poverty of friends such as Katya. At the end of the section, he has developed a close friendship with Dmitri Nekhyudov, which seems to largely involve putting right the world's wrongs.

We discussed future life, art, government service, marriage and the education of children, and it never entered our heads that all we said was most awful nonsense. This did not occur to us because the nonsense we talked was clever and pleasing nonsense and in youth we still value intellect and believe in it.

In the "Youth" section, Nikolai starts to develop his own set of morals and ideas on how to live life, which he expresses in his "Rules of Life" book. Despite the increasing presence of religion in his life, he starts to find it difficult to maintain his ideals when his father remarries and Nikolai begins to fail at university. The book finishes with Nikolai resolving to rewrite his "Rules of Life" book.