Background <p>Cannabis use initiation is highly common among youth. Harm reduction in cannabis use (HR-c) has proven effective in minimizing the potential harms of the substance. However, its adoption by health and social services (HSS) practitioner’s remains limited owing to several obstacles. This study marks the final phase of a broader research initiative. It aims to: (1) present the implementation of a knowledge translation (KT) plan developed to enhance HR-c adoption and formulate actionable strategies to support its applicability; and (2) evaluate its immediate and short-to-medium-term effects.</p> Methods <p>Ziam et&#xa0;al.’s (2024) evaluation framework guided our description of the KT plan implementation and our evaluation of its effects. Using a non-probabilistic sampling method, we recruited managers and practitioners from four residential facilities for youth in Quebec (<i>N</i> = 19). Two KT strategies – policy briefs and deliberative dialogues – were implemented, during which participants co-developed final actions to optimize HR-c adoption. A mixed-methods evaluation followed, involving a questionnaire with five scales and semi-structured interviews. Data were analyzed using post-parallel analysis, combining descriptive statistics and thematic analysis to assess the KT plan’s implementation and effects. Cronbach’s alpha of the subscales was calculated to assess their internal consistency.</p> Results <p>The final actions formulated with participants addressed HR-c, youth and organizations. Quantitative findings revealed: (1) a high appreciation for the deliberative dialogues; (2) positive attitudes toward HR-c; (3) negative attitudes toward abstinence-based treatments; (4) participants’ favourable perception of their training level in HR-c; and (5) a strong intention to implement the proposed actions. The qualitative findings revealed that participants were using the transferred knowledge (e.g., HR-c strategies applicable by youth) and planned to disseminate the formulated actions within their teams to enhance practices.</p> Conclusions <p>A systematic and multidirectional KT process was implemented to optimize HR-c adoption among HSS practitioners working with youth in Quebec, serving as a model for similar interventions. The study reinforced HR-c applicability, facilitated its adoption and contributed to the formulation of concrete implementation actions. Future research should examine the long-term impact of KT initiatives on HR-c adoption and explore strategies to support practitioners in applying the transferred knowledge.</p>