The federal Senior Community Service Employment Program (SCSEP) provides on-the-job training to people 55 years and older with incomes at or below 125% of the federal poverty level with multiple barriers to employment. This study examined the processes by which SCSEP may influence participant financial, physical, and mental well-being. We engaged 15 SCSEP participants and case managers over four virtual and one telephone session using a participatory research method called community-based system dynamics. Activities included identifying key problem trends, variable elicitation, developing a causal map, and identifying changes to the system to increase participant well-being. Respondents identified how individual, organizational, and program and policy factors relate to participant well-being (e.g., SCSEP participation reduces social isolation, which increases desire to participate) and suggested program and policy recommendations to strengthen SCSEP (e.g., benchmarks of success should include health and well-being outcomes). These findings highlight the benefits and potential of this long-running program.