Background and ObjectivesTransdiagnostic approaches have been promoted as a means of maximising preventative effects across multiple problems with depression and anxiety suitable targets as they appear to have highly interconnected systems in pathology development and maintenance. This study investigated long-term effects of two universal school-based programs, Emotion Regulation (ER) and Behavioral Activation (BA), that sought to prevent depression and anxiety by targeting worry (a transdiagnostic feature) to promote resilience. MethodsThis follow-up study captured data from 162 of 316 initial students (aged 8-13; 52.2% female), from six Australian schools. The original study design cluster randomised students by school into BA, ER, or a usual class control. Intervention conditions consisted of 8 x 50-minute weekly sessions. This study measured the effects of these interventions after 24 months on resilience, worry, depression, and anxiety. Resilience was also examined as a potential mediator. ResultsAt 24-month follow-up, there was no significant effect of either intervention on depression, anxiety, worry, or resilience levels. Significantly fewer participants in ER and BA met clinical thresholds for separation anxiety disorder (SAD) and obsessive-compulsive disorder (OCD) in the 24-month follow-up compared with baseline. No mediation effects were found. LimitationsAlthough self-report measures are common in universal, school-based research, this represents a study limitation. ConclusionsBoth interventions may provide limited long-term protective effects on SAD and OCD symptoms, which appear to have a shelf-life shorter than 24 months. To maintain program effects, refresher sessions at shorter intervals may be a consideration for future research.