Pediatric firearm-related injuries pose a significant public health problem in the United States, yet the associated financial burden has not been well described. This is the first study examining national data on the cost of initial hospitalization for pediatric firearm-related injuries. In this retrospective review, the Healthcare Cost and Utilization Project Kids' Inpatient Database from the years 2003, 2006, 2009, and 2012 was used to identify all patients 18 years of age and under who were admitted with firearm-related injuries. We compared demographic and discharge-level data including injury severity score, hospital length of stay, income quartile, injury intent, and inflation-adjusted hospital costs across age groups (0-5, 6-9, 10-15, 16-18 years). There were approximately 4,753 pediatric firearm-related admissions each year, with a median hospitalization cost of $12,984 per patient. Annual initial hospitalization costs for pediatric firearm injuries were approximately $109 million during the study period. Pediatric firearm-related injuries predominately occured among older teenagers (74%, 16-18 years), males (89%), black individuals (55%), and those from the lowest income quartile (53%). We found significant cost variation based on patient race, income quartile, injury severity score, intent, hospital length of stay, disposition, and hospital region. Inflation-adjusted hospitalization costs have increased significantly over the study period (p < 0.001). Pediatric firearm-related injuries are a large financial burden to the United States healthcare system. There are significant variations in cost based on predictable factors like hospital length of stay and injury severity score; however, there are also substantial discrepancies based on hospital region, patient race, and income quartile that require further investigation.