ObjectivesTraumatic injury surveillance can be enhanced by describing injury severity trends. This study reports trends in work‐related injury severity for males and females over the period 2004–2017 in Ontario, Canada.MethodsA weighted measure of workers' compensation benefit expenditures was used to define injury severity, obtained from the linkage of workers' compensation claims to emergency department (ED) records where the main injury or illness was attributed to work. Denominator counts were obtained from Statistics Canada's Labor Force Survey. Trends in the annual incidence of injury, classified as low, moderate, or high severity, were examined using regression modeling, stratified by age and sex.ResultsOver a 14‐year observation period, there were 1,636,866 ED records included in the analyses. Overall, 57.6% of occupational injury records were classified as low severity, 29.5% as moderate severity, and 12.8% as high severity conditions. There was an increase in the incidence of high severity injuries among females (annual percent change (APC): 1.52%; 95% CI: 0.77, 2.28), while the incidence of low and moderate severity injuries generally declined for males and females. Among females, injuries attributed to animate mechanical forces and assault increased as causes of low, moderate, and high severity injuries. The incidence of concussion increased for both males (APC: 10.51%; 95% CI: 8.18, 12.88) and females (APC: 16.37%; 95% CI: 13.37, 19.45).ConclusionThe incidence of severe work‐related injuries increased among females in Ontario between 2004 and 2017. The methods applied in this surveillance study of traumatic injury severity are plausibly generalizable to applications in other jurisdictions.