This research aims to explore in depth the opinions of classroom teachers about primary school mathematics textbooks. For this aim, the relevant research was carried out with a phenomenological pattern within the framework of a qualitative research approach. The study group of this research was determined by convenience sampling technique in line with purposeful sampling. Hence, the study group of this research consists of 14 classroom teachers. A semi-structured interview form was used as a data collection tool in the research. The interviews were conducted face-to-face by the researcher. The data obtained was analyzed according to the descriptive analysis technique. Accordingly, the opinions of the classroom teachers who participated in this research about primary school mathematics textbooks were determined as 1) Content, 2) Program, 3) LanguageExpression, 4) Skills, 5) Visual Design, 6) Measurement and Evaluation, and 7) Values. The participants made some suggestions to improve the quality of primary school mathematics textbooks. These are listed as 1) Content, 2) Skills, 3) Visual Design, 4) Measurement and Evaluation, and 5) Values. In line with the findings obtained, the researcher concluded that in order for primary school mathematics textbooks to become more qualified, the books should be prepared by experts in the field and with a multiple approach.