Posttraumatic sciatic nerve palsy associated with severe pain, swelling in the gluteal region, elevated tissue pressures, and diffuse edema of the gluteal musculature documented by computed tomography (CT) occurred in a 22-year-old man. Diffuse muscle swelling was observed intraoperatively, and sciatic nerve function returned within days following surgical decompression. This case represents an acute gluteal compartment syndrome, and this entity should be included in the differential diagnosis of posttraumatic sciatic nerve palsy.