Background: Intervention construct validity procedures test the efficacy of a program to impact on targeted theory constructs. Purpose: To examine the intervention construct validity of the Planning to be Active (PBA) and Mentored Planning to be Active (MPBA) programs on high school youth residing in Appalachia. Methods: Twenty high schools in Appalachia were randomly assigned to either the teacher lead PBA program or the peer mentor led MPBA program. All participants (n = 633) completed a set of valid and reliable instruments assessing SCT variables: social support for exercise friends, social support for exercise family, self-efficacy for exercise and the self-regulation skills (behavioral goal setting, exercise self-monitoring, building social support, overcoming barriers, and self-reward). Results: PBA and MPBA are effective approaches to increasing social support, self-efficacy for exercise and increasing the use of self-regulation skills to increase physical activity. The results identify constructs that were not improved suggesting areas for curriculum refinement. Discussion: PBA and MPBA have established construct validity. Intervention construct validity methods identified program strengths and weaknesses. Translation to Health Education Practice: Intervention construct validity is an evidence-based approach to program improvement. Intervention construct validity establishes a foundation for testing theory impact on health behaviors.