Tonio is a young boy, son of a north German merchant and a southern mother with artistic talents. He has inherited qualities from the both sides. During his school days, he is in love with his classmate, the athletic and handsome Hans Hansen.
He is a very sensitive person and that causes him trouble. He can feel things more deeply than others can, which results in school absenteeism and poor grades.
At age of sixteen, Tonio falls in love with Ingeborg Holm, a very beautiful, blond girl which he knows all his life, but it is now that she noticed her.
When he grows up, he becomes a famous writer, who lives in southern Germany. But, his life changes when he returns to his hometown.
In this book we follow the life of Tonio Kröger, from his childhood to his adulthood. We see his growing up, his developing and changing as a person. We see a person who fights with his feelings his entire life, being pulled between the German bourgeoisie and the art; also, being pulled between two worlds from sexual aspect, as a child, he experiences homosexual love and later, as a teenager, he experiences heterosexual love.