The aim of the study is to examine the explanations of the primary and middle school mathematics teacher about misconceptions. In this study, the teachers' opinions were taken about what misconception is and underlying causes of these misconceptions. The study was conducted totally with 8 teachers, 4 primary teachers and 4 middle school mathematics teachers of them working in primary and middle school in Bartın province in the 2015-2016 academic year. In the study, qualitative approach basedcase study was used. As data collection tool, interview form consisting 6 questions was used. Having been collected with semi-structured interview technique, the obtained data were taken to the audio record. In the analysis of data, qualitative data analysis techniques were used. As a result of the study, it was seen that the majority of both primary teachers and middle mathematics teachers had difficulty in expressing what misconception is and the reasons for these misconceptions. In particular, it was determined that they could not explain exactly cause of pedagogic basedmisconceptions such as 0 adding side-on multiply a number with 10, lack of effect of zero next comma. In light of the obtained results, suggestions which develop instructional explanations about misconceptions of the teachers were made.