Regional Access Project Foundation (RAP) is a nonprofit funder that instituted a Mental Health Initiative (MHI), with the goal of enhancing mental health quality of life in Eastern Riverside County (California) through grantmaking. RAP partnered with HARC, a nonprofit research organization, to design and conduct a collective impact evaluation of the work being done under the MHI grants. HARC created measurement tools pertaining to mental health quality of life, access, stigma, and impact of services. HARC trained each of RAP’s eight grantees on data collection and database management. Collective impact results showed that the wellbeing of clients significantly increased, including those at risk for depression. There were no significant changes in access to mental healthcare or stigma, but reasons for this were illuminated. Overall, every eight out of ten clients reported a positive impact on their relationships with others. Challenges experienced during the collective impact evaluation are shared.