Background: Psychiatrically vulnerable adolescents may be at heightened risk for suicide during the COVID-19 pandemic. This study characterizes suicidal ideation (SI) and suicide attempts (SA) in a sample of adolescents psychiatrically hospitalized during COVID-19. Rates of SI and SA are compared to a historical hospital sample from a matched period in the year prior. Associations between specific stressors and COVID-related SI are also explored. Methods: This cross-sectional chart review utilizes hospital intake data, including self-reports of SA, SI (general and COVID-related), and COVID-specific stressors. Results: SA and SI ratings were higher in the COVID-19 sample compared to the historical sample. Stressors related to missing special events, financial problems, in-home conflict, and changes in living circumstances were associated with COVID-related SI. Among first-time admissions, several interpersonal stressors were linked to COVID-related SI. Limitations: Analyses were cross-sectional, limiting our ability to draw conclusions about causality. Conclusions: This study offers preliminary evidence that COVID-19 may be contributing to suicidal thoughts and behaviors in high-risk adolescents.