AIM: To evaluate the retinal vessel diameters in patients with migraine by optical coherence tomography (OCT). METHODS: In this cross-sectional study, 124 eyes of 62 patients with a diagnosis of unilateral migraine during attack-free period and 42 age- and sex-matched control subjects were included. Migraine patients were divided into the ≤2 migraine attacks per month group and the ≥5 migraine attacks per month group. All subjects underwent complete ophthalmological and neurological examinations before measurements. Retinal vessel diameters and choroidal thickness were examined with the Spectralis OCT. RESULTS: The mean diameters of the arteries in the eyes on the headache side of control group, ≥5 migraine attacks per month and ≤2 migraine attacks per month group at 480 µm from the optic disk (Raster 3) were 119.54±46.69, 136.68±25.93 and 119.34±31.75 µm respectively with a steady decline to 105.57±32.15, 118.18±31.87 and 108.05±38.77 µm at 1440 µm (Raster 7), the last measurement point, respectively. The retinal artery diameter measurements were significantly increased in ≥5 migraine attacks per month patients at four out of five measured points compared to control group (P<0.05). There were no statistical differences at any of the points of vein measurements. The choroidal thickness measurements were significantly decreased in ≥5 migraine attacks per month patients at all measured points compared to control group (P<0.05). CONCLUSION: The retinal artery diameter is found to increase significantly and the choroidal thickness is found to decrease in the eyes on the headache side in ≥5 migraine attacks per month patients compared to control group.