Thyroid eye disease (TED) is the most common cause of proptosis in adults. The external manifestations of TED are characteristic and the diagnosis is typically made without imaging. Although there are multiple descriptions of primary and secondary orbital tumors initially mistaken for TED in the literature, there are limited reports detailing the findings of patients with long-standing TED whom developed an orbital tumor at a later date. Herein, we present a 6-year retrospective multi-center report of three patients with long-standing TED who developed an initially unsuspected orbital or cavernous sinus tumor.