Sexual and gender minority (SGM) individuals experience high rates of homelessness and criminal justice system involvement, underscoring the need for supportive housing services. To explore the service needs of this population, we interviewed providers (n = 11) and clients (n = 10) from eight supportive housing organizations working with SGM populations in Los Angeles County, California, USA. We used the Consolidated Framework for Implementation Research to synthesize interview responses into themes (by domain and cross-cutting). Takeaways included the need for investment in systems of care for vulnerable SGM populations; the particular marginalization of Trans individuals and providers that serve them; the roles of supportive housing staff, residents, and leadership in cultivating an affirming environment; the prevalence of discrimination and stigma within supportive housing programs and broader society; and the complex interrelationships among SGM identity, homelessness, and criminal justice system involvement. These findings have important implications for supportive housing services and related policy.