We present the case of an 18-year-old girl with McCune Albright Syndrome (MAS) and a near total mandibular defect reconstructed with a free fibula flap. There are three reports of mandibular reconstruction in a patient with MAS using the free fibula flap; however this case is unique for two reasons. One, the continuity defect in our patient was much larger than previously reported, representing nearly the entire length of the mandible (21 cm) and required the entire harvestable length of the fibula. Two, the progression of the patient's disease limited options for reconstruction and dictated the use of a fibula with small dysplastic changes.