© 2018 The Obesity Society Objective: The Study of Novel Approaches to Weight Gain Prevention (SNAP) trial demonstrated that two self-regulatory interventions prevented weight gain in young adults. Weight and shape concern (WSC) at baseline was evaluated as a moderator of weight outcomes at 24 months. Methods: Young adults (n = 599) were randomized to self-regulation with small changes (to create 200 kcal/day deficit), self-regulation with large changes (to facilitate preemptive weight loss of 5-10 lb), or self-guided control. WSC was assessed by using one item from the Eating Disorders Assessment. ANOVA was used to examine whether the association between baseline level of WSC and percent weight change over 24 months differed across treatment conditions. Results: Approximately 22% of participants reported high WSC (37% moderate; 41% low). WSC and treatment condition interacted to influence weight change at 24 months (P = 0.03). Individuals with high WSC gained weight in the large changes group (WSC least squares means ± SE, high: + 0.73% ± 1.19%; moderate: −2.74% ± 0.84%; low: −2.41% ± 0.79%). The small changes condition was particularly effective for those with high WSC (high WSC: −2.49% ± 1.16%; moderate: −0.60% ± 0.88%; low: −0.71% ± 0.80%). WSC did not impact weight change among control participants. Conclusions: Individuals with high WSC may benefit from a small-changes approach to weight gain prevention. These findings indicate WSC may be used to match individuals to weight gain prevention treatment conditions.