Orbital metastases are rare and predominantly unilateral occurrences. Bilateral metastases affecting the extraocular muscles are extremely rare. A few case reports of bilateral metastases to extraocular muscles described binocular diplopia with conspicuous bilateral external ophthalmoplegia as an initial symptom. We report a case in which unilateral ptosis was an initial symptom and bilateral incomplete ophthalmoplegia was found on initial neurologic examination in invasive ductal carcinoma of the breast. The patient had hormone receptor-positive breast cancer, and so was treated by hormonal therapies and closely monitored. The presence of a secondary orbital lesion presents many difficulties of differential diagnosis and treatment. A thorough neurologic examination to detect ocular manifestations is most important for localization and broad differential diagnosis including mechanical orbital metastatic lesion.