The aim of this study is to determine the mathematical concepts in children's books. The examined books were selected by looking at the preference rates of the books in the library located in the city center according to their class levels. A set of ten books from the 2nd grade, 3rd grade and 4th grade levels were determined by the criterion sampling method. The book chosen for the 2nd grade is a series called Ünlülerle Bir Gün-1. The book chosen for the 4th grade is the series named Kurtuluşun Kahramanları. Because one series of the 3rd grade book set consists of five books, the second and fourth series were examined. The books chosen for the 3rd grade are Türkiye’yi Geziyorum 2 and Türkiye’yi Geziyorum 4 which are belong to Levent series. Since no data could be obtained about the most preferred books at the 1st grade level, 10 books with 5 or more editions were selected and a total of 40 books were examined. The books chosen for the first grade consist of the books in the sets named Çağlar'ın Maceraları, Elif’in Maceraları and İnci'nin Maceraları. Descriptive analysis was used to examine the collected data. Themes were first created within the framework of 3 basic learning areas in the Ministry of National Education's Mathematics Teaching Program. The 3 main learning areas consist of numbers and operations, geometry and measurement themes. Then sub-themes were created. The sub-themes consist of spatial relationships, comparison, sorting, matching, counting, addition, subtraction, multiplication, division, fraction, length measurement, liquid measurement, weight, area measurement, time and money. As a result of the research, it was determined that the concepts in the measurement category were included the most. It was determined that the measurement category was followed by the concepts of the numbers and operations category. Finally, it has been determined that the concepts in the geometry category are less frequently used among these concepts.