AbstractThis study analyzes the influence of Canadian provincial governance structures on support services for older adults with intellectual and developmental disabilities. Following multilevel governance (MLG) literature, it compares Ontario's more centralized governance structure with Québec's more disentangled multi‐jurisdictional structure by how they promote social inclusion—a guiding policy priority for disability and aging services. Despite their divergent MLG structures, the findings show that when accounting for implementation effects, Ontario and Québec are producing strikingly similar social inclusion outcomes, owing to the similar motivations of frontline workers. Interviewees in both provinces prioritized needs related to health and medication use, to the detriment of social inclusion goals, reflecting the “siloization” of aging and disability support services. Respondents also stressed the impracticality of person‐centered care within current funding models, thus defending divergence from a central policy priority in both provinces. This points to the importance of accounting for the input of policy implementers, whose resistance to overarching policy priorities confound structural differences in the production of policy outcomes.