Background: Veterans with serious mental illness (SMI) have high rates of homelessness and may require unique supports. Impairments in executive functions (EFs) such as emotion regulation, planning, and decision making are common in this population, interfere with negotiation of real-world problems leading to housing loss, and have been linked to negative behaviors which can result in homelessness. There is a need to intervene to improve EFs among homeless Veterans with SMI with the goal of increasing housing stability. Interventions exist but have not yet been adapted for or tested with homeless Veterans with SMI. Significance/Impact: VA has dedicated significant resources to homeless services, and considerable research efforts have been devoted to identifying factors linked to poor housing and community integration outcomes. Although there is abundant evidence that [decision making and related] EFs are impaired in individuals who are homeless, live with SMI, or both, and that this impacts a person's ability to attain and retain housing, interventions to improve EFs have not been adapted, tested, or implemented with homeless Veterans. This proposal addresses the HSR&D Major Priority Domains of Mental and Behavioral Health and Healthcare Equity and Health Disparities, and the High-Priority Research Topics of vulnerable populations, intersection of vulnerable populations, and impact of social determinants of health on outcomes of care. Innovation: The BrainWise program, which will be adapted and pilot tested in this study, is an effective critical thinking intervention which has demonstrated benefits in various populations of youth and adults including homeless men, but to our knowledge has not been administered to persons with SMI or to Veterans. Specific Aims: (1.) Adapt an effective critical thinking group intervention (BrainWise) for use with homeless- experienced Veterans with serious mental illness, utilizing key stakeholder feedback; (2.) In a pilot trial with Veterans with serious mental illness enrolled in a Homeless Patient Aligned Care Team clinic, study the feasibility, acceptability, and fidelity of the adapted intervention; (3.) Assess the feasibility of proposed methods for measuring of executive functions, knowledge of BrainWise content, housing history, and substance use in the study sample, and obtain descriptive statistics to inform a subsequent larger study. Methodology: We will interview key stakeholders (clinicians and administrators from HPACT and HUD- VASH, and Veteran patients) about the BrainWise curriculum in order to inform the adaptation of the program's content and delivery. We will then deliver the adapted intervention to [two simultaneous groups] of 8–12 homeless Veteran participants with SMI over the course of 8–10 weekly group intervention sessions. Focus groups will be conducted immediately after each intervention session in order to solicit Veteran feedback about the intervention. A final focus group will be hel...