Background/aim: To evaluate the effect of intravitreal pro re nata (PRN) ranibizumab treatment from the start on the best-corrected visual acuity (BCVA) and the central retinal thickness (CRT) in macular edema (ME) due to branch retinal vein occlusion (BRVO). Materials and methods: Patients with ME secondary to BRVO, who were treated on a PRN basis after a single intravitreal ranibizumab injection, were retrospectively evaluated. The main outcome measures were changes in BCVA and CRT as measured by optical coherence tomography. Results: The number of injections over 6 months was 2.43 ± 1.16. The mean BCVA of the patients was 0.84 ± 0.10 logMAR at baseline and 0.41 ± 0.06 at the 6th month (P 6lt; 0.001). Mean BCVA of the ischemic BRVO group was 1.06 ± 0.68 logMAR at baseline and 0.44 ± 0.30 logMAR at the 6th month (P < 0.05). Similarly, the mean BCVA of the nonischemic BRVO group was 0.77 ± 0.53 logMAR at baseline and 0.41 ± 0.36 logMAR at the 6th month (P < 0.05). Between groups, there was no significant difference in mean BCVA at any examination. Conclusion: Intravitreal ranibizumab is a safe and effective treatment option for ME due to ischemic and nonischemic BRVO using PRN from the start.