Background: The review examined the effectiveness of Active Support (RQ1) and stakeholders' experiences of the model (RQ2). Method: Data were meta-analysed (RQ1; studies = 14) and synthesized narratively (RQ2; studies = 10). Results: By follow-up (6 months post-training), effect sizes (RQ1) for resident total activity engagement were significant and ranged from small (d = 0.33, 95% CIs: 0.10-0.50) to large (Tau-U = 0.95, 95% CIs: 0.64-1.25) depending on study design. Follow-up changes in staff assistance were moderate (d = 0.56, 95% CIs: 0.23-0.89; Tau-U 0.63, 95% CIs: 0.32-0.93) and large for quality of support (d = 1.03, 95% CIs: 0.61-1.44). Other outcomes did not change. Conclusions: Active Support was more effective following complete staff training, in larger settings, at lower staff-to-resident ratios and with less experienced staff. Active Support training and outcomes were valued by staff and residents (RQ2), and staff experienced increased job satisfaction. Lower staff turnover and organizational readiness appear crucial for maintaining implementation.