There is growing recognition in research and policy of a mental health crisis among Canada’s paramedics but despite this, epidemiological surveillance of the problem is in its infancy. Just weeks before the emergence of the COVID-19 pandemic, we surveyed paramedics from a single, large, urban paramedic service in Ontario, Canada to assess for clinically significant symptoms of Post-Traumatic Stress Disorder (PTSD), depression, and anxiety and to identify potential risk factors for each. In total, we received 589 completed surveys (a 97% completion rate) and found that 11% met the screening criteria for PTSD, 15% for depression, and 15% for anxiety, with 1 in 4 active-duty paramedics meeting the criteria for any of the three as recently as February 2020. In adjusted analyses, the risk of a positive screen varied as a function of employment classification, gender, self-reported resilience, and previous experience as a member of the service’s peer support team. Our findings support the position that paramedics have high rates of current mental illness – a problem likely to have worsened since the onset of the COVID-19 pandemic. We echo the calls of researchers and policymakers for urgent action to support paramedic mental health in Canada.