Serious mental illnesses (SMIs), such as a schizophrenia-spectrum disorders, bipolar and related disorders, personality disorders, and the most severe presentations major depressive, obsessive compulsive, and other psychological disorders are believed to affect approximately 5% of adults in the U.S. (Substance Abuse and Mental Health Services Administration in Results from the 2010 national survey on drug use and health: mental health findings, 2012). Older adults who have SMIs experience higher rates of health problems and mortality, increased feelings of isolation and loneliness, and report lower levels of life satisfaction and overall well-being compared to individuals of the same age who do not have SMIs. Despite these disparities, limited intervention research focuses on addressing specific needs of older adults with SMIs. While growing evidence supports “PERMA” wellbeing theory and its related interventions (Donaldson et al. in J Posit Psychol, 16(6):811–818, 2021. https://www.tandfonline.com/doi/full/10.1080/17439760.2020.1818813), to-date the existing intervention research for older adults with serious mental illnesses has not been oriented by the PERMA wellbeing theory framework or used promising, related positive psychology interventions. Therefore, the aim of the research presented in this report was to determine feasibility and acceptability of a wellbeing course delivered to older adults with SMIs in a psychosocial clubhouse. The course was framed by wellbeing theory and infused with theoretically based, evidence-informed interventions, and was specifically designed for older adults with SMIs. Participants were English-speaking adults over the age of 50 who had SMI diagnoses and were members of the psychosocial clubhouse where the course was offered. Feasibility and acceptability were evaluated using qualitative data and attendance records. Thematic analysis of the qualitative data developed insights into what was most useful in the course and what its drawbacks and limitations were. These results represent an important step in the development of a novel and innovative wellbeing-focused approach to enhancing quality of life for older adults with SMIs, as well as expanding psychosocial clubhouse offerings for their older adult members.