Purpose: The purpose of this paper is to understand how a Canadian intervention based on a professional development (PD) model did or did not influence schools' capacities to absorb a Healthy School (HS) approach into their operations. This study is the second part of a research project: previously published results regarding this research provided a detailed description of the PD model and highlighted the relevance and effectiveness of PD in improving actors' HS-related knowledge and practices. The present paper focuses on the organizational impact of such PD intervention. Design/Methodology/Approach: The design was based on a realist evaluation approach, which helps to elicit a theory explaining how an intervention leads to particular outcomes. A multi-site case study of three schools with pre-(T[subscript 0]) and post-(T[subscript 1]) intervention comparison was adopted. Multiple qualitative methods were used to capture how the changes were achieved by collecting data from various stakeholders involved in the intervention. Findings: The PD model tested reinforced the schools' capacities to absorb this type of initiative. For one of the capacities examined, "exploitation", i.e., the ability to incorporate and maintain the initiative into schools operation, the evidence was less apparent. In congruence with the realist evaluation, the results are rendered in the form of a contextualized intervention theory identifying the links between the PD and the mechanisms that were likely necessary to explain what led to the changes in "absorptive" capacities (which refers to the capabilities of schools to acquire and assimilate HS knowledge, and also to transform and exploit them, in the context). Originality/Value: The refined theory, based on empirical findings, can enable facilitators and practitioners to gain a deeper understanding of the action mechanisms shown to be determining in the success of HS implementation.