Medullary thyroid cancer (MTC) is a neuroendocrine tumor derived from parafollicular or C cells of the thyroid gland. Surgical resection is the mainstay of treatment for MTC. External-beam radiation treatment (EBRT) has traditionally played a limited role in the management of MTC. Despite aggressive surgery, patients at high risk for local recurrence may benefit from adjuvant EBRT. With improvements in radiation technique, adequate dose can be effectively delivered to the region at risk while minimizing dose to surrounding critical structures. Although the role of EBRT in the management of these tumors has thus far been poorly defined, EBRT should be considered as a treatment option for patients with locally advanced MTC to optimize locoregional control.