Amid global aging trends and persistent challenges in volunteer retention for hospitalized older adults, this study investigated how volunteers’ management and perceived organizational support influence re-participation intention through the mediating role of participation efficacy. Based on achievement need theory, we analyzed 549 valid responses from Chinese volunteers using PLS-SEM. Key findings were as follows: (1) Both management and organizational support directly enhance re-participation intention while exerting significant indirect effects via participation efficacy; (2) participation efficacy can predict re-participation intention. The study found participation efficacy’s mediation role, proposing actionable strategies to strengthen volunteers’ management and support systems.