Purpose: Medication beliefs are likely contingent on aspects of health literacy: knowledge, motivation, and competences to access, understand, appraise, and apply health information. An association between medication beliefs and health literacy is expected as they both influence self-management. The aim of this study was to examine the association between health literacy and the beliefs about overuse and harmful effects of medication and to examine modifying effects of age, gender, and number of medications on this association. Methods: The data were collected using the online “Medication panel” of the Dutch Institute for Rational Use of Medicine. A linear regression model was used to examine the association between health literacy and beliefs about medication and the modifying effects of age, gender, and number of medications on this association. Results: Respondents with a lower level of health literacy had more concerns about overuse (β adj.= -.174, p<.001) and harmful (β adj.= -.189, p<.001) effects of medication. This study found no modifying effects. Conclusions: A lower health literacy level is associated with more concerns about the overuse and harmful effects of medication. The results of this study suggest that extra attention should be given to persons with low health literacy level by healthcare professionals, to decrease their concerns about overuse and harmful effects, and improve adherence to self-management behavior.