<p>Young adults with Adverse Childhood Experiences (ACE), e.g., household dysfunction and maltreatment) are at high risk for poor health outcomes such as mental health and substance use disorders. The COVID-19 pandemic imposed numerous external stressors and impacted access to mental healthcare services for many individuals. This study explores mental health, substance use and mental healthcare experiences among ACE-exposed young adults during the COVID-19 pandemic. Young adults (<i>N</i> = 26, ages 21–29 years old, 15 males, 9 females, and 2 non-binary) who experienced ACE were recruited online to learn about their histories of substance use, anxiety, depression, and mental healthcare experiences during COVID-19. After interviews via Zoom, transcription was completed and thematic analysis was conducted. Thematic analyses revealed several factors impacting young adults’ substance use and mental health behaviors during the pandemic. Young adults with a history of ACE experienced the following: isolation, grief and loss, financial and employment disruption, problematic interpersonal relationships that were exacerbated by staying home, and health-related anxiety. Taken together, these experiences impacted their substance use, mental health and mental healthcare services. Young adults who experienced ACE indicated that substances helped alleviate feelings of anxiety and depression. However, young adults who received mental healthcare during the pandemic reported that such care benefited them in reducing symptomology. Future pandemic responses should include a focus on mental healthcare for young adults at risk for substance use and mental health problems.</p>