BACKGROUND: Millions of people seek emergency department (ED) care for injuries each year, the majority for minor injuries. Little is known about the effect of psychiatric co-morbid disorders that emerge after minor injury on functional recovery. This study examined the effect of post-injury depression on return to pre-injury levels of function. METHOD: This was a longitudinal cohort study with follow-up at 3, 6 and 12 months post-injury: 275 adults were randomly selected from those presenting to the ED with minor injury; 248 were retained over the post-injury year. Function was measured with the Functional Status Questionnaire (FSQ). Psychiatric disorders were diagnosed using the Structured Clinical Interview for DSM-IV-TR disorders (SCID). RESULTS: During the post-injury year, 18.1% [95% confidence interval (CI) 13.3-22.9] were diagnosed with depression. Adjusting for clinical and demographic covariates, the depressed group was less likely to return to pre-injury levels of activities of daily living [odds ratio (OR) 8.37, 95% CI 3.78-18.53] and instrumental activities of daily living (OR 3.25, 95% CI 1.44-7.31), less likely to return to pre-injury work status (OR 2.37, 95% CI 1.04-5.38), and more likely to spend days in bed because of health (OR 2.41, 95% CI 1.15-5.07). CONCLUSIONS: Depression was the most frequent psychiatric diagnosis in the year after minor injury requiring emergency care. Individuals with depression did not return to pre-injury levels of function during the post-injury year.