OBJECTIVES/HYPOTHESIS: To describe the presentation and management of acute complicated mastoiditis in children. STUDY DESIGN: Retrospective case series. METHODS: An analysis of pediatric patients with acute complicated mastoiditis treated at an urban, tertiary care children's hospital from 2007 to 2014 was performed. RESULTS: Forty-eight patients presented with a total of 67 complications of acute mastoiditis. Mean age at presentation was 4.8 years (range = 0.1-15.3 years). The most common complications were subperiosteal abscess (n = 22, 45.8%), epidural abscess (n = 16, 33.3%), and sigmoid sinus thrombosis (n = 14, 29.2%). The most common pathogens isolated included Streptococcus pneumoniae (n = 14, 29.2%) and group A streptococcus (n = 10, 20.8%). Multidrug resistance was not associated with complication type. Surgical management included myringotomy +/- tympanostomy tube placement in 46 (95.8%) patients (the only surgery in 10), drainage of subperiosteal abscess without mastoidectomy in 18 (37.5%) patients, and mastoidectomy in 21 (43.8%) total patients. Patients presenting with intracranial complications were the most likely to undergo a mastoidectomy. Anticoagulation was used in the management of nine of 14 (64.3%) patients presenting with sigmoid sinus thrombosis. Neurosurgical interventions (n = 7, 14.6% patients) were primarily performed to manage increased intracranial pressure. CONCLUSIONS: Subperiosteal abscess was the most common complication of acute mastoiditis, and when occurring as the sole complication was successfully managed with antibiotics and surgical intervention that did not include mastoidectomy. Epidural abscess and sigmoid sinus thrombosis were more prevalent than reported in prior series and were managed more aggressively. These patients were more likely to need neurosurgical interventions. LEVEL OF EVIDENCE: 4. Laryngoscope, 127:2321-2327, 2017.