Importance The appropriate treatment of children with mild traumatic brain injury (mTBI) and intracranial injury (ICI) on computed tomographic imaging remains unclear. Evidence-based risk assessments may improve patient safety and reduce resource use. Objective To derive a risk score predicting the need for intensive care unit observation in children with mTBI and ICI. Design, Setting, and Participants This retrospective analysis of the prospective Pediatric Emergency Care Applied Research Network (PECARN) head injury cohort study included patients enrolled in 25 North American emergency departments from 2004 to 2006. We included patients younger than 18 years with mTBI (Glasgow Coma Scale [GCS] score, 13-15) and ICI on computed tomography. The data analysis was conducted from May 2015 to October 2016. Main Outcomes and Measures The primary outcome was the composite of neurosurgical intervention, intubation for more than 24 hours for TBI, or death from TBI. Multivariate logistic regression was used to predict the outcome. The C statistic was used to quantify discrimination, and model performance was internally validated using 10-fold cross-validation. Based on this modeling, the Children's Intracranial Injury Decision Aid score was created. Results Among 15 162 children with GCS 13 to 15 head injuries who received head computed tomographic imaging in the emergency department, 839 (5.5%) had ICI. The median ages of those with and without a composite outcome were 7 and 5 years, respectively. Among those patients with ICI, 8.7% (n = 73) experienced the primary outcome, including 8.3% (n = 70) who had a neurosurgical intervention. The only clinical variable significantly associated with outcome was GCS score (odds ratio [OR], 3.4; 95% CI, 1.5-7.4 for GCS score 13 vs 15). Significant radiologic predictors included midline shift (OR, 6.8; 95% CI, 3.4-13.8), depressed skull fracture (OR, 6.5; 95% CI, 3.7-11.4), and epidural hematoma (OR, 3.4; 95% CI, 1.8-6.2). The model C statistic was 0.84 (95% CI, 0.79-0.88); the 10-fold cross-validated C statistic was 0.83. Based on this modeling, we developed the Children's Intracranial Injury Decision Aid score, which ranged from 0 to 24 points. The negative predictive value of having 0 points (ie, none of these risk factors) was 98.8% (95% CI, 97.3%-99.6%). Conclusions and Relevance Lower GCS score, midline shift, depressed skull fracture, and epidural hematoma are key risk factors for needing intensive care unit-level care in children with mTBI and ICI. Based on these results, the Children's Intracranial Injury Decision Aid score is a potentially novel tool to risk stratify this population, thereby aiding management decisions.