Methotrexate is a commonly used agent in the treatment of an un-ruptured ectopic pregnancy. Thromboembolic events are rarely seen side effects of such a medicine. We report the case of the 22-year-old woman who underwent Methotrexate therapy for an un-ruptured ectopic pregnancy without any history of thromboembolic risk factors. A second dose (50 mg/m(2)) was administered to the patient showing a non-decreasing pattern of beta-HCG levels after an initial standard dosage of Methotrexate (50 mg/m(2)). On the 12th day of the treatment, a sudden onset of painless vision loss was seen in the right eye. Fundal imaging and fluorescein angiography revealed an occlusion of the superior temporal branch of the right retinal artery. After a month of hyperbaric oxygen therapy, complete recovery without loss of vision was achieved.