Davorin Trstenjak is a Croatian pedagogist that was active in 19th and 20th century. During his active time as a teacher, he wrote informative books on education, most of which are analysed in this thesis. Books that got analysed and deconstructed are: Mladi učitelj, Zreo učitelj, Slobodna škola, Uzgoj čovjeka, Kulturni uzgajatelji and Darvinizam u uzgoju. By using these books, the ways in which the author perceives education and educational processes in schools is established, as well as his attempts to improve them. Each book is specific; however, the greatest pedagogical value can be found in Mladi učitelj and Zreo učitelj, due to the fact that they give concrete didactic instructions to the reader. Slobodna škola is an extremely important book, as it is focused on the autonomy of schools and negative elements that hinder the development of education. Kulutnih uzgajatelja, Uzgoja čovjeka i Darvinizma u uzgoju are specific because the author uses them to cover vast array of topics which are not exclusively pedagogical. All of the mentioned books have distinct similarities which are highlighted and those similarities will help to determine the fundamentals of Trstenjak's work and for what type of education he stood for. Other philosophers and pedagogists that directly affected author's work and opinions are mentioned. The author affected the school system in several ways, especially in aspects of education and upbringing. His books are presented, analysed, described and are used to conclude what type of pedagogist and teacher Trstenjak was. His influence is visible in the modernization of the school system, secularization and implementation of progressive ideas, which are founded on the fact that an individual undergoes educational processes for its own betterment, as well as its environment.