Purpose To evaluate the changes in the choroidal structure in the setting of retinal vein occlusion (RVO). Methods Changes in the structure of the choroid were studied in sixty-four eyes with unilateral central or branch RVO using optical coherence tomography (OCT) with enhanced depth imaging and OCT-angiography (OCT-A). Choroidal vascularity index (CVI), Haller layer/choroidal thickness (H/C) ratio, and choriocapillaris flow density were used to compare the structural characteristics of the choroid with fellow eyes and the eyes of thirty-four age-, gender-, and systemic co-morbidity-matched controls. Results Eyes with RVO had a higher H/C ratio but a lower choriocapillaris flow density compared to both fellow and control eyes (p < 0.001). CVI was significantly lower in both eyes of the patients with RVO compared with control eyes (p < 0.05) with a more robust decrease in the eye that had developed RVO (p < 0.001). The H/C ratio (r = 0.303p < 0.001), CVI (r = - 0.268,p = 0.001), and choriocapillaris flow density (r = - 0.237,p = 0.003) were all correlated with logMAR visual acuity, and other clinical features. Conclusion Retinal vein occlusions alter the hemodynamic properties of the choroid leading to structural changes. These changes may be secondary to a compensatory mechanism to supply oxygen to hypoxic retina.