This study presents evidence that the second wave of COVID-19 cases and subsequent community-wide lockdown in the state of Victoria during winter of 2020 contributed to worsening mental health, elevations in psychological distress and changes in a number of important determinants of health including work, healthcare and social interactions. Similar lockdowns are now occurring around the globe to reduce transmission of SARS-CoV-2, and are likely to occur in the future as large-scale outbreaks continue to occur. Our findings suggest that in addition to lockdown measures, governments imposing such restrictions need to focus on improving access to mental health supports and healthcare services, providing financial assistance to communities and supporting social interactions.