Objective To investigate whether patients’ psychological well-being (depression, quality of life, body image satisfaction) and functioning (self-efficacy for eating and exercising behaviours and food cravings) improve 12 months after bariatric surgery and whether self-compassion is associated with better psychological outcomes and lower weight after bariatric surgery. Design Longitudinal, prospective observational study. Methods Bariatric patients (n = 126, 77.8% female, 46.4 ± 10.8 years) completed the Self-compassion Scale, Center for Epidemiology Studies Depression Scale, Impact of Weight on Quality-of-Life questionnaire, Body Image Scale, Weight Efficacy Lifestyle Questionnaire, Spinal Cord Injury Exercise Self-Efficacy Scale, and G-Food Craving Questionnaire pre-operatively and 12 months post-operatively. A medical professional measured patients’ weight during each assessment. Data were analysed using repeated measures t-tests and multivariate regression analyses with Benjamini–Hochberg correction for multiple testing. Results Patients’ BMI, depression, and food cravings decreased significantly after surgery while quality of life, body image satisfaction, and self-efficacy to exercise improved. Higher self-compassion was associated with lower post-operative depression, greater quality of life, higher body image satisfaction, and better self-efficacy for eating behaviours (p-values <.05) but not with post-operative BMI, self-efficacy to exercise, or food cravings. Conclusions Even though pre-operative self-compassion was not directly associated with a lower 12-month post-operative BMI, it had a positive relationship with patients’ post-operative well-being and self-efficacy for controlling eating behaviour. In turn, this could help patients to manage their health long after bariatric surgery. Further work regarding the role of self-compassion on long-term health outcomes would be worthwhile.