Despite the fact that community mental health programs have adapted to become more participatory and consumer-driven, evaluations of these programs continue to rely on traditional hierarchical evaluation methods. Additionally, participatory evaluations that do exist often involve higher-powered stakeholders, such as program staff and funders, and exclude stakeholders with traditionally less power but “high legitimacy” – the program participants. Unfortunately, even fewer examples of participatory evaluations exist with program participants who are highly vulnerable and experiencing mental illness, substance abuse, and/or homelessness. This presentation will examine the unique challenges and benefits of conducting a participatory evaluation with highly vulnerable clients in a consumer-driven Housing First program. It will demonstrate that in addition to better fitting program values and producing more ecologically valid results, taking a participatory approach to evaluations with vulnerable groups can enhance program effects, increase client empowerment, and lead to multi-level change.