The present study examines the factors affecting citizenship education, such as school, environment, students, teachers, and the curriculum, as perceived and experienced by secondary school teachers. The study is qualitative and uses a phenomenological design. Maximum diversity sampling was used for selecting participants. The sample consisted by eight teachers of geography, history, and philosophy who worked in three different secondary schools in the Sahinbey district of Gaziantep province in the 2017-2018 academic year. The data was collected through semi-structured interview forms and analyzed through content analysis. The data revealed causality relations. The results of the study reveal that participants categorized the concept of citizenship and citizenship education as individual, state, rights, and responsibility, which is in line with the literature. All of the participants carried out studies on citizenship knowledge and skills during their teaching processes. It was discovered that citizenship education is realized through informal (unplanned) education together with curriculum content. According to participants, citizenship education is affected by various positive and negative factors such as students, teachers, and the curriculum. [This paper was presented at the 6th International Congress on Curriculum and Instruction, 11-13 October 2018, in Kars, Turkey.]