This study will take place at four outpatient clinics serving adults with serious mental illness. Informed consent will be obtained from N=80 individuals with a Diagnostic and Statistical Manual of Mental Illnesses (DSM)-5 diagnosis of schizophrenia or schizoaffective disorder meeting inclusion/exclusion criteria to participate in a randomized controlled trial comparing Motivation Skills Training (MST) to a Healthy Behaviors Control (HBC) group. Eligible participants will receive a baseline assessment including sociodemographic and psychosocial assessments, measures of motivation, goal attainment, and quality of life, as well as measures of executive skills, community functioning, and psychiatric symptoms severity. Both MST and HBC will be implemented as once weekly group therapies. The treatment phase is approximately 12-14 weeks. MST will focus on motivation knowledge and self-regulation skills while HBC will focus on physical health and health-related skills.