Objective To identify associations between specific types of mental illness (occurring alone or in combination with other mental illness) and (specific and all types) of injury. Methods Analyses involve 21 027 employees aged 18–64 insured by Deseret Mutual Benefit Administrator (DMBA), 2020. Nine classifications of mental illness and 12 classifications of injury are considered. Rate ratios are adjusted for age, sex, and marital status. Results The rate of injuries is 13.6%. A positive association exists between any mental illness and injury (rate ratio [RR] = 1.74, 95% CI 1.62–1.87). The positive association is consistent across all types of injury, except burns. While having a mental illness tends to positively associate with having an injury (vs. none), it more strongly associates with having two or more types of injury (vs. none). Injury rates are significantly greater when comorbid mental illness is involved (vs. one type of mental illness), more so for multiple types of injuries. Specifically, there is a positive association between having a mental illness (vs. none) and a single type of injury (vs. none) (RR = 1.58, 95% CI 1.42–1.75) or two or more types of injuries (vs. none) (RR = 1.94, 95% CI 1.70–2.23). Corresponding estimates where comorbid mental illnesses exist (vs. none) are (RR = 2.07, 95% CI 1.70–2.51) and (RR = 3.32, 95% CI 2.64–4.17), respectively. The most common combinations of mental illness that positively associate with injury tend to involve comorbid mental illness. Conclusions Several types of mental illness positively associate with injury and are more strongly associated when there is comorbid mental illness.