Perfectionism and inflated responsibility have both been identified as risk factors for the development and maintenance of obsessive-compulsive (OC) symptoms. The aim of the present study was to test whether the relationships between these two variables and OC symptoms are mediated by the misinterpretation of intrusive thoughts (MIT). Three hundred and three university students completed the Frost Multidimensional Perfectionism Scale, the Maudsley Obsessional Compulsive Inventory, the Responsibility Attitude Scale, and the Responsibility Interpretations Questionnaire. MIT was found to partially mediate the relationship between responsibility attitudes and OC symptoms. MIT also partially mediated the relationship between concern over mistakes and OC symptoms, even after controlling for responsibility attitudes. Both concern over mistakes and responsibility attitudes were significant predictors of MIT and OC symptoms, but responsibility was the stronger predictor when all of the variables were included in the model. Clinical implications for the treatment of OCD are discussed.