Background: Emergency service workers (ESWs) are at increased risk of experiencing mental health symptoms. Little is known about the health impact of providing informal care to ESWs (e.g., their family and friends). Objectives: We aimed to examine the health of Australian ESWs and their informal caregivers compared to the general population, using baseline data from ESWs enrolled in an intervention study. Methods: Outcomes included psychological distress, sleep, quality of life and physical activity.