Physical activity promotion in the academic classroom (PAPAC) is an effective means for increasing children's school-based physical activity. In the context of a South Carolina policy requiring elementary schools to provide children with 90 min of physical activity beyond physical education every week, the purpose of this study was to test a theoretical model of elementary classroom teachers' (ECT) PAPAC adoption drawing from Rogers' (1995) diffusion of innovations theory and a social ecological perspective. ECTs (N = 201) were assessed on their policy awareness, perceived school support for PAPAC, perceived attributes of PAPAC, domain-specific innovativeness, and self-reported PAPAC. Partial least squares analysis supported most of the hypothesized relationships. Policy awareness predicted perceived school support, which in turn predicted perceived attributes and domain-specific innovativeness. Perceived compatibility, simplicity, and observability, and domain-specific innovativeness predicted self-reported PAPAC. This study identifies variables that should be considered in policy-driven efforts to promote PAPAC adoption.