BACKGROUND Stress may indirectly contribute to disease (e.g. cardiovascular disease, cancer) by producing deleterious changes to diet. PURPOSE The purpose of this study was to test the effectiveness of a stress management support (SMS) tool to reduce stress-related unhealthy snacking and to promote stress-related healthy snacking. METHODS Participants were randomized to complete a SMS tool with instruction to link stressful situations with healthy snack alternatives (experimental) or a SMS tool without a linking instruction (control). On-line daily reports of stressors and snacking were completed for 7 days. RESULTS Daily stressors were associated with unhealthy snack consumption in the control condition but not in the experimental condition. Participants highly motivated towards healthy eating consumed a greater number of healthy snacks in the experimental condition on stressful days compared to participants in the experimental condition with low and mean levels of motivation. CONCLUSIONS This tool is an effective, theory driven, intervention that helps to protect against stress-induced high-calorie snack consumption.