A 6-year-old boy presented with a pontine abscess initially misdiagnosed as brainstem glioma, but he deteriorated rapidly and developed new symptoms of respiratory distress. Magnetic resonance (MR) imaging revealed a rapidly growing mass lesion in the pons. Microsurgical evacuation of the abscess via a suboccipital retromastoid approach resulted in neurological improvement and resolution of the lesion on MR images. Brainstem abscess can be successfully treated with early, accurate diagnosis based on MR imaging and appropriate microsurgical and antibiotic management.