The free fibula osteocutaneous flap has been widely used in the reconstruction of facial bone, especially the mandible. Donor-site morbidity for free fibula osteocutaneous flap is generally considered to be low and minor. However, a severe and rare complication, osteofascial compartment syndrome (OCS), should be paid more attention to after the harvesting of the fibula osteocutaneous flap. In this report, we described a case where the OCS occurred in 56-year-old man after fibula osteocutaneous flap was transplanted for mandible reconstruction, and its treatment is reported. We suggest that if free fibula osteocutaneous flap is used, the OCS of the leg should be considered seriously, and the drainage must be effective and adequate.