Fun For Wellness is a self-efficacy theory-based online behavioral intervention developed to promote growth in well-being and physical activity by providing capability-enhancing opportunities to participants. Evidence has been provided for the efficacy of Fun For Wellness to promote subjective well-being in adults in a relatively controlled setting. The objective of this study was to evaluate the effectiveness of Fun For Wellness to increase subjective well-being in adults with obesity in the United States of America in a relatively uncontrolled setting. The data described in this manuscript were collected within a more broadly focused trial: the Well-Being and Physical Activity Study (ClinicalTrials.gov, identifier: NCT03194854, 