In this study, it was tried to determine what the criteria used by English teachers working at different school levels in the selection of course materials and textbooks, and what the similarities and differences were in the selection of course materials between different levels. Although the study is a descriptive study, it was carried out in accordance with the phenomenological research pattern, one of the qualitative research designs. Prior to the study, written consent was obtained from the Gaziosmanpasa University Social and Humanity Studies Committee with Meeting decision number 11.18 on 21.05. 2021 and Protocol Number: E-33490967-044-41105. The participants of the study consist of 51 English language teachers, 15 from primary, 17 from secondary, and 19 from high schools. The opinions of the participants were taken by using a semi-structured guided interview form. Content analysis of the data obtained from the participants were done in a way to create codes and themes, and they were transformed into tables. According to the findings obtained from the study, "visual richness" was the criterion used by the majority of the participants (f=36), regardless of the level in the selection of course materials. Secondly, while primary school teachers prefer fun and up-to-date materials, it is seen that secondary school teachers pay attention to age-appropriateness and entertaining materials. It was observed that participants working at high school level with different priorities expressed similar views. Regarding the textbook selection criteria of English language teachers, visuality was stated as the primary criterion in primary and secondary education, while teachers working at the high school level paid more attention to the way the subjects were taught. The teachers should pay attention to students’ ages, genders, levels, interests and goals in language learning while choosing textbooks.