Abstract Recent studies suggest that weight suppression (WS), defined as the discrepancy between current and highest past weight, predicts short-term weight gain in bulimia nervosa (BN) during treatment. The current study was designed to build on this preliminary work by examining the relation between WS and long-term weight change in BN. Treatment-seeking women ( N = 97) with DSM-IV BN participated in a naturalistic longitudinal follow-up study of eating disorders. At intake, height and weight were measured and highest past weight was assessed. Self-reported weights were collected every 6 months for 5 years. Hierarchical Linear Modeling (HLM) estimated growth curves for weight change over time. Significant inter-person variability was detected for intercepts and slopes ( P < 0.001) so both were treated as random effects. Participants' weights increased over the study course, moderated by baseline WS ( P < 0.001), such that higher WS predicted more rapid weight gain. Weight change was not associated with entry weight, height, or highest-ever weight, suggesting that WS per se predicted weight change. These findings complement previous short-term studies in BN by demonstrating that WS predicts weight gain over 5 years. Because weight gain could spur radical dieting that maintains BN, these results have important treatment implications.