OBJECTIVE: Interventions in post-disaster environments may be accelerated by identifying protective behavioral factors adding incremental value to models of psychopathology using longitudinal methods. One protective behavior applicable to post-disaster contexts is behavioral activation (BA). BA is defined here as a behavioral pattern involving presence of valued activity engagement. While relevant post-disaster, the incremental value of BA behaviors in predicting longitudinal post-disaster outcomes is not well understood. We hypothesized that higher baseline engagement in behaviors consistent with a BA framework would predict decreased posttraumatic stress disorder (PTSD) symptom severity, depression symptom severity, and sleep disturbance approximately 3, 6, and 12 months after hurricane survivors completed baseline measures. METHODS: The current study is a secondary analysis from a randomized controlled trial of a disaster mental health digital intervention. Participants completed surveys at baseline and approximately 3, 6, and 12 months post-enrollment. Correlations and hierarchical regression analyses were calculated following data screening to predict PTSD symptom severity, depression symptom severity, and sleep disturbances. RESULTS: Controlling for alcohol use, prior trauma, displacement, and intervention condition, higher baseline BA consistently predicted less PTSD symptom severity, depression symptom severity, and sleep disturbances. CONCLUSION: Results suggest that post-disaster interventions should consider addressing BA. The study provides evidence that BA is potentially an important protective factor longitudinally predicting sleep disturbances and psychopathology after natural disasters.