PURPOSE: This study provides information on how the coronavirus disease 2019 (COVID-19) outbreak is affecting emerging adults currently or recently homeless in terms of engagement in protective behaviors, mental health, substance use, and access to services. METHODS: Ninety participants in an ongoing clinical trial of a risk reduction program for homeless, aged 18-25 years, were administered items about COVID-19 between April 10 and July 9, 2020. RESULTS: Most participants reported engaging in COVID-19 protective behaviors. Past week mental health symptoms were reported by 38%-48% of participants, depending on symptoms. Among those who used substances before the outbreak, 16%-28% reported increased use of alcohol, tobacco, and marijuana. More than half of the participants reported increased difficulty meeting basic needs (e.g., food), and approximately 32%-44% reported more difficulty getting behavioral health services since the outbreak. CONCLUSIONS: Innovative strategies are needed to address the increased behavioral health needs of young people experiencing homelessness during events such as the COVID-19 outbreak.