Objective: Appearance-related interpretation bias is postulated to play a role in the maintenance of body dissatisfaction, a risk factor for body dysmorphic disorder (BDD) and eating disorders (ED). Cognitive Bias Modification for Interpretation (CBM-I) has been shown to reduce interpretation bias and symptoms in emotional disorders. This study investigated the acceptability and efficacy of web-based, appearance-related CBM-I for body dissatisfaction in a three-armed randomized controlled trial.Methods: Participants with high body dissatisfaction (N = 318) were randomized to multi-session CBM-I (Sentence Word Association Paradigm, SWAP, with feedback) vs. control (SWAP without feedback) vs. waitlist condition. Body dissatisfaction, BDD symptoms, self-esteem, depression and quality of life were assessed at baseline and post-intervention. Symptoms were monitored up to one-week and four-week follow up. We further investigated video-based stress reactivity at post-intervention.Results: CBM-I led to a differential pre-post increase in adaptive interpretation patterns, particularly for appearance-related and social situations (d = 0.65-1.18). Both CBM-I and control training reduced body dissatisfaction, BDD symptom severity and depression. However, CBM-I (vs. control and waitlist) improved appearance-related quality of life (d = 0.51), self-esteem (d = 0.52), and maladaptive appearance-related beliefs (d = 0.47). State stress reactivity was overall reduced in the CBM-I group (vs. waitlist). Intervention effects largely held stable up to follow-up. Treatment satisfaction for appearance-related CBM-I was comparable to other CBM-I studies, with overall low rates of adverse reactions. Discussion: These findings support assumptions of cognitive-behavioral models for body dissatisfaction, BDD and ED, and suggest that CBM-I is an efficacious and acceptable intervention.