Hashimoto's encephalopathy is defined by the coexistence of encephalopathy and antithyroid antibodies. We report two cases of adult-onset temporal lobe epilepsy with subacute cognitive decline, high titers of antithyroid antibodies, multi-antiepileptic drug hypersensitivity, and good response to immunomodulatory treatment. The relevance of multidrug hypersensitivity in the setting of adult-onset epilepsy and the importance of searching for autoimmune causes for epilepsy are discussed.