The aim of this study is to identify misconceptions of nine grade students on the topic of repeating decimal numbers. Data were obtained from forty students through “Diagnostic Test of Repeating Decimal Numbers” including open-ended questions. Questions were prepared according to the classification of misconceptions as overgeneralization, overspecialization, mistranslation and limited conception. As a part of rational numbers unit the topic of “representation of repeating decimals” is introduced at 6, 7, 8 and 9 grades in our schools. In spite of this, findings of this study illustrate that even nine grade students still have some common misconceptions about this topic. Findings illustrated that most students’ misconceptions were based on overgeneralization. In addition to this students also shared the other categories of misconceptions as well.