Aim. To analyze the subfoveal choroid thickness and choroidal volume in unilateral ocular ischemic syndrome (OIS). Methods. A retrospective review was conducted for all patients with unilateral OIS from October 2010 through June 2014. The subfoveal choroidal thickness (SFChT) and choroidal volume of both eyes were compared. Results. 19 unilateral OIS patients were included in this study. The mean SFChT of OIS eyes was significantly lower than that of fellow eyes (OIS eyes: 208.89 ± 82.62 μm and fellow eyes: 265.31 ± 82.77 μm, P<0.001). The choroidal volume of OIS eyes was significantly smaller than that of fellow eyes (OIS eyes: 0.16 ± 0.05 mm3 and fellow eyes: 0.21 ± 0.05 mm3, P<0.001). Conclusion. The choroidal thickness and volume of OIS eyes were smaller than those of unaffected fellow eyes. Decreased choroidal circulation caused by carotid artery stenosis might affect the discordance of choroidal thickness and choroidal volume.