This study aims to determine the reliability of scores obtained from self-, peer-, and teacher-assessments in terms of teaching materials prepared by teacher candidates. The study group of this research constitutes 56 teacher candidates. In the scope of research, teacher candidates were asked to develop teaching material related to their study. One class teacher and two teacher candidates (peers) randomly selected from the class took part in rating the teaching materials prepared by each teacher candidate. In addition to teacher- and peer-assessments, all teacher candidates who had prepared materials assessed their own material using the same criteria. The form used by the teacher, individuals, and two peers for rating teaching materials contains 10 criteria. Generalizability theory (G-theory) was used to determine the reliability of scores obtained from the self-, peer-, and teacher-assessments related to the teaching materials that teacher candidates had prepared. According to the results of the research, an insignificant difference between rater types was determined, and the reliability of scores obtained from self-, peer-, and teacher-assessments on teaching materials is within acceptable limits.