Children and adolescents with attention-deficit/hyperactivity disorder (ADHD) are prone to sustaining trauma that requires emergency department (ED) admission. Methylphenidate (MPH) can reduce ADHD symptoms and may thus theoretically reduce the risk of trauma-related ED admission, but previous studies do not make this association clear. This study examines this association. A total of 17 381 patients aged 6 to 19 years who received MPH prescriptions were identified by using the Clinical Data Analysis & Reporting System (2001-2013). Using a self-controlled case series study design, the relative incidence of trauma-related ED admissions was compared with periods of patient exposure and nonexposure to MPH. Among 17 381 patients prescribed MPH, 4934 had at least 1 trauma-related ED admission. The rate of trauma-related ED admission was lower during exposed periods compared with nonexposed periods (incidence rate ratio [IRR]: 0.91 [95% confidence interval (CI): 0.86-0.97]). The findings were similar only when the incident trauma episode was assessed (IRR: 0.89 [95% CI: 0.82-0.96]). A similar protective association was found in both genders. In validation analysis using nontrauma-related ED admissions as a negative control outcome, no statistically significant association was found (IRR: 0.99 [95% CI: 0.95-1.02]). All sensitivity analyses demonstrated consistent results. This study supports the hypothesis that MPH is associated with a reduced risk of trauma-related ED admission in children and adolescents. A similar protective association was found in both male and female patients. This protective association should be considered in clinical practice.