Motor vehicle crashes (MVCs) are a leading cause of death among children. Multivariable analyses of age-appropriate child restraint system (CRS) use in the "booster-aged" population are needed. The current study identified factors associated with age-appropriate CRS use in fatal MVCs for children 4 to 7 years old, using 2011 to 2015 data from the Fatality Analysis Reporting System. Of 929 MVC fatalities, 32% of fatally injured children were in an age-appropriate restraint. While age-appropriate CRS use was higher for 4-, 5-, and 6-year-olds relative to 7-year-olds (adjusted relative risk [aRR] = 2.57, 2.51, and 2.18, respectively; p < .01 for each comparison), black children (aRR = 0.62; p < .01) relative to white children, and drivers who had not used a lap-shoulder belt (aRR = 0.40; p < .01) relative to belted drivers were associated with lower levels of age-appropriate CRS use. Our findings underscore the continued importance of communicating best practice guidelines on CRSs to caregivers of young children.