The COVID-19 pandemic has hit humanity globally. Besides its obvious threats to our physical health and economic stability, one can only speculate about the pandemic’s and its countermeasures’ psychosocial impacts. Here, we took advantage of a sample of healthy male participants who had completed psychosocial measures on mental health, environmental concern, and prejudice against asylum-seekers just before and during the nationwide lockdown in Germany in spring 2020. A follow-up assessment of 140 participants during the lockdown provided a unique opportunity to track psychosocial changes in a prospective longitudinal study design. In comparison to before the lockdown (1) mental health worsened, (2) environmental concern increased, and (3) prejudice against asylum-seekers decreased. Our study demonstrates psychosocial “side effects” of the pandemic that bring both challenges and opportunities for our society with regard to the handling of psychological reactions to this pandemic and further global crises, including climate change and mass migration.