Objective: Few studies have tested the purported causal mechanisms between social participation and health, especially among those in poor health. This study aimed to determine whether self-management of chronic disease operates as a pathway through which social participation affects health-related quality of life. Method: I utilized causal mediation analysis among 600 low-income older Singaporeans living with chronic conditions, to test whether self-management mediates the association between social participation and health-related quality of life. Results: Results show that self-management fully mediated the positive effect of informal social participation on health-related quality of life. Formal social participation was found to have a negative direct effect on health-related quality of life. Discussion: These findings reiterate the primacy of family and friends for older adults, but highlight that a better understanding of formal engagement with the low-income population is still needed.