Background: To evaluate the effect of a single intravitreal ranibizumab injection in eyes with acute nonarteritic ischemic optic neuropathy (NAION). Subjects and Methods: In this retrospective clinical data analysis, 17 eyes of sixteen patients who experienced a visual loss with duration of 15 days or less comprised the study group. In addition to standard ophthalmic examination, retinal nerve fiber layer thickness (RNFLT) analysis with spectral domain OCT was also performed prior to 0.5 mg Ranibizumab injection, one week, one, three, six months and one year after the injection. Results: The mean time between visual loss and intravitreal injection was 7.5 days (Range, 2-15 days). Mean age of patients was 59 years (Range, 41-90 years). Male to female ratio was 6:10. After a single dose of ranibizumab injection, visual gain was noted in 14 of 17 study eyes. In two eyes, visual acuity was minimally reduced and no change was noted in the remaining eye with an initial visual acuity of hand motions. While pre-injection mean best-corrected visual acuity (BCVA) was 1.45 ±0.88 log Mar unit, post-injection mean BCVA was 1.00±0.68, 0.86 ±0.70, 0.80 ±0.71, 0.77 ±0.70, 0.77 ±0.70 log Mar unit respectively at the first week, first month, third month, sixth month and first year. In all patients, the mean RNFLT dramatically decreased after the injection during the follow- up. While pre-injection mean RNFLT was 210 ±38 μm, post-injection mean RNFLT was 162.11±40.2, 94±27, 71.23±22.5, 63 ±19 and 57 ±18 μm respectively at the first week, first month, third month, sixth month and first year. No injection related complication was noted during the follow-up period. Conclusion: Intravitreal ranibizumab injection can be a treatment modality in eyes with acute NAION. © Saatci et al.