Behavioral weight loss interventions are often delivered in groups. Group cohesion may enhance program attendance and, thereby, weight loss. In this secondary analysis, our goals were to: (1a) assess whether group cohesion measured early in a behavioral weight loss intervention predicts program attendance and weight loss outcomes and, if so, (1b) explore whether attendance mediates the link between group cohesion and weight loss; (2) characterize the association between change in group cohesion and weight loss throughout the intervention. Veterans (n = 324) initiated a 16-week, group-based behavioral weight loss program involving biweekly in-person group visits. In linear regression models, early group cohesion was unrelated to group attendance or weight loss. Although group cohesion significantly increased during the intervention, this change was not associated with weight loss. These findings are consistent with the limited literature; however, they are inconsistent with theoretical assertions and clinical observations of the influence of group factors on outcomes.