The study analyzes the effects of grade retention on the development of mathematics competence and on motivation and beliefs in the field of mathematics using data from a representative sample of 9th graders in Germany (PISA 2012 and repeated measurement one year later). Same-age comparisons were applied between a group of retained students (N = 89) and a matched comparison group of promoted students (N = 89), applying the method of Propensity Score Matching (PSM). The results show no different effects in the development of mathematics competence between retained students and promoted students. Concerning motivation and beliefs in the field of mathematics the retained students significantly increased their mathematics work ethics compared to the promoted group. However, no group specific effects could be found for mathematics interest, self-efficacy, instrumental motivation, and behavior.