To evaluate factors associated with the diagnosis of open-angle glaucoma (OAG) after a retinal vein occlusion (RVO). Retrospective, cross-sectional study. Patients diagnosed with OAG after RVO were matched 2:1 with RVO patients without prior glaucoma. Logistic regression identified factors linked to OAG diagnosis. Of 1178 RVO patients without initial OAG, 51 (4.5%) were later diagnosed with OAG after an average of 5.5 ± 6.1 years. Screening tests for OAG were performed at a higher frequency in patients diagnosed with OAG compared with patients who never received this diagnosis (visual field [VF] testing 21.6% versus 10.8% (P = 0.073) and retinal nerve fiber layer [RNFL] imaging 52.9% versus 27.4% (P = 0.002), respectively). At the time of the first VF obtained after RVO, mean deviation averaged -10.3 dB in the affected eyes, compared with -5.0 dB in the fellow eyes (P < 0.001); in contrast, RNFL thickness was similar between eyes at the time of OAG diagnosis (72 µm versus 74 µm, P = 0.290). Predictive factors for OAG diagnosis included higher intraocular pressure (IOP) and cup-to-disc ratio (CDR) in the unaffected eye, and the absence of macular edema in the RVO-affected eye (R2 = 0.375, P < 0.001). OAG is a significant risk factor for RVO. Our study reveals a reciprocal relationship between RVO and the development of OAG, highlighting the need for glaucoma risk assessment in all patients with RVOs to avoid delays in diagnosis and vision loss from glaucoma.