Purpose: Sexual and gender minority youth (SGMY, ages 16-24 years) face disparities in sexually transmitted infections (STIs) and HIV, in part, due to exposure to settings and behaviors that may harm youth's physical and mental health. This study examines the scope of sexual health and HIV services available to youth living with serious mental illness (SMI), including SGMY, seeking care at publicly funded outpatient mental health programs. Methods: Between 2018 and 2019, we surveyed 183 managers of mental health programs serving youth living with SMI of ages 16-24 years, including SGMY, in San Diego and Los Angeles counties. Participants reported on programs' target populations, sexual health/HIV service provision, and the use of peer providers. Descriptive statistics and Pearson chi-square tests were used to describe sexual health/HIV services and identify programmatic characteristics associated with providing these services. Results: Overall, 46% of all programs surveyed provided sexual health/HIV services. Of these, 62% provided HIV education, 81% provided sexual/reproductive health education, and 69% provided sexual/reproductive health education tailored for lesbian, gay, bisexual, queer, intersex (LGBQI) youth. Peers often provided these services. Chi-squared tests showed that programs employing peer specialists (p = 0.009) and targeting LGBQI youth (p = 0.045) were significantly more likely to provide sexual health/HIV services. Conclusion: The use of peer providers may reduce stigma around sexual/HIV service utilization and promote SGMY's trust. Publicly funded outpatient mental health programs serving youth and especially those actively engaging SGMY may consider also offering onsite HIV, STI, and sexual health services, creating a one-stop-shop approach.