The purpose of the study is to investigate chemistry student teachers’ levels of understanding and alternative conceptions concerning chemical equilibrium. The study was conducted with totally 97 chemistry student teachers (16 from first grade, 15 from second grade, 22 from third grade, 22 from fourth grade and 22 from fifth grade) who are enrolled in the department of secondary science education of Fatih Faculty of Education at KTU. A test, consisting of 13 two-tier multiple choice questions, was used to collect data. The first tier is a question with three choices, while the other tier involves four possible reasons for all possible answers in the first tier. The questions in the test were taken from literature related to chemical equilibrium. The results of the present study confirmed many alternative conceptions that had been identified in previous studies and showed that fourth-year student teachers are more successful than the other classes.