Abstract Purpose Previous research on obesity surgery (OS) showed that patients do not only experience weight loss but also improvements in certain mental health outcomes (e.g., depression) after OS. However, self-harm behaviors might increase after OS. Regarding self-harm, the literature is mostly limited to studies using data from hospital or emergency room charts. This longitudinal study examined self-reported self-harm behaviors and potential psychopathological correlates before and after OS. Materials and Methods Pre-surgery patients (N = 220) filled out a set of questionnaires before and approximately six months after OS. Self-harm behaviors were captured with the Self-Harm Inventory. The assessments further included standardized instruments to measure symptoms of depression, anxiety, eating disorders, alcohol use, and suicidal ideations. Results Any self-harm was reported by 24.6% before and by 25.0% after OS. No differences in the number of self-harm behaviors or prevalence of any self-harm before and after OS were found. Overall, 11.4% experienced self-harm behaviors at both times. A subset showed self-harm behaviors only before (13.2%) OS and another subset only after OS (13.6%). These two groups were about the same size. Self-harm behaviors showed strong associations with psychopathology after OS, especially with depression and suicidal ideation. Conclusion No increase in self-harm behaviors after OS emerged. Still, a subgroup showed self-harm behaviors after OS closely linked to further psychopathology. This mirrors the need to implement screening for self-harm before and after OS into OS care. Further studies with longer follow up periods are needed to extend these findings. Graphical Abstract