Evidence suggests that post-secondary students without pre-existing mental health concerns may have experienced worsening mental health during the COVID-19 pandemic, relative to students with pre-existing mental health concerns. To clarify the psychological impacts of the pandemic, and elucidate why differences may exist among students, 20 interviews were conducted with emerging adults enrolled in university. Using directed content analysis, eight themes were identified: three more common among students with pre-existing mental health concerns, three more common among students without pre-existing mental health concerns, and two shared. Although all students experienced novel stressors during the pandemic, students without pre-existing mental health concerns reported greater increases in social and academic isolation, relative to students with pre-existing mental health concerns. Students with pre-existing mental health concerns also leveraged existing coping repertoires, which further supported their ability to manage pandemic-related challenges. Findings highlight how postsecondary institutions can bolster student well-being.