Background: Anaplastic thyroid cancer (ATC), while rare, carries a uniformly poor prognosis. Current treatment includes surgery when possible, radiotherapy, and chemotherapy. Multiple chemotherapeutic agents are in the process of clinical testing, and promising agents include those in the tyrosine kinase inhibitor family. Our patient represents a novel case of ATC treated with sunitinib, one such tyrosine kinase inhibitor. Methods/Results: We utilized the experimental sunitinib in conjunction with radiation therapy to treat a patient with aggressive ATC in whom curative resection was unable to be achieved due to carotid sheath and tracheal involvement. The patient had marked clinical response and sustained stable disease for 8 months, which coincides with reported data regarding sunitinib to treat other thyroid malignancies. Conclusion: Our case illustrates the efficacy of sunitinib therapy as a possible adjunct in the treatment of ATC