Treatment of the severely traumatized or mangled lower extremity poses significant challenges. The Mangled Extremity Severity Score (MESS) is a scale that uses objective criteria to assist with acute management decisions. Most research on the MESS has been in adults or combined series with few children. The study was performed to investigate the MESS in children exclusively. The MESS was applied retrospectively to 36 patients with grades IIIB and IIIC open lower extremity fractures collected from two level 1 pediatric trauma centers. Patients were divided into limb salvage and primary amputation groups based on the decision of the treating surgeon. In the salvage group there were 18 grade IIIB fractures and 10 grade IIIC fractures. The MESS prediction was accurate in 93% of the injured limbs. In the amputation group eight limbs met the inclusion criteria; the MESS agreed with the treating surgeon in 63% of cases. These findings suggest the MESS should be considered when managing a child with severe lower extremity trauma.