Pediatric injury is both common and expensive. Finding ways to prevent pediatric injury is a major public health concern. Many studies have investigated various aspects of pediatric injury, and some suggest that birth order may be an important risk factor for pediatric injury. This study further examined the relationship of birth order with pediatric injury, specifically studying the association of birth order with emergency department-attended infant injury while adjusting for other important family and individual covariates. Data for analysis included Utah birth certificate, death certificate, and hospital emergency department datasets, which were probabilistically linked to obtain complete demographic and injury information for infants born in 1999—2002. Three groups of risk factors were defined for analysis: maternal demographics, maternal risk behaviors, and infant demographics. Two outcome variables were defined for this study, “injury event” and “severe injury event.” Data was analyzed using generalized estimating equations (GEE). Birth order was associated with infant injury events and severe infant injury events. Birth order 4th or greater had the greatest effect for both injury outcomes. Additionally, several maternal characteristics were associated with infant injury events and severe infant injury events. In particular, maternal age and maternal smoking behavior were associated with increased infant injury risk. This study identified two targeted populations that are well-suited to injury prevention efforts: infants born to mothers who smoke, and infants born to mothers who are young and have many other children.