Objectives Serious mental illness is common among those who have experienced a physical workplace injury, yet little is known about mental health service use in this population. This study aims to estimate the proportion of the workplace musculoskeletal injury population experiencing a mental illness, the proportion who access mental health services through the workers’ compensation system and the factors associated with likelihood of accessing services.

Methods A longitudinal cohort study was conducted with a random sample of 615 workers’ compensation claimants followed over three survey waves between June 2014 and July 2015. The primary outcome was receiving any type of mental health service use during this period, as determined by linking survey responses to administrative compensation system records for the 18 months after initial interview.

Results Of 181 (29.4%) participants who met the case definition for a serious mental illness at one or more of the three interviews, 75 (41.4%) accessed a mental health service during the 18-month observation period. Older age (OR=0.96, 95% CI 0.93 to 0.99) and achieving sustained return to work (OR=0.27, 95% CI 0.11 to 0.69) were associated with reduced odds of mental health service use. Although not significant, being born in Australia was associated with an increased odds of service use (OR=2.23, 95% CI 0.97 to 5.10).

Conclusions The proportion of injured workers with musculoskeletal conditions experiencing mental illness is high, yet the proportion receiving mental health services is low. More work is needed to explore factors associated with mental health service use in this population, including the effect of returning to work.