AIM: To investigate sectoral changes in the mean peripapillary choroidal thickness (PCT) in patients with unilateral branch retinal vein occlusion (BRVO). METHODS: This retrospective, interventional study included 41 patients with acute, unilateral BRVO without macular edema. All patients completed at least a 6-month follow-up period. The PCT was measured at eight locations (temporal, superotemporal, superior, superonasal, nasal, inferonasal, inferior, and inferotemporal). In addition to calculating the average of all locations, the peripapillary choroidal area was divided into four sectors: superior (average of superotemporal PCT, superior PCT, and superonasal PCT), temporal, inferior (average of inferotemporal PCT, inferior PCT, and inferonasal PCT), and nasal. RESULTS: In the BRVO-affected eyes, the mean PCT was 177.7±69.8 μm (range, 70.1-396.0 μm) at baseline and 127.8±54.8 μm (range, 56.4-312.1 μm) at 6mo (P<0.001). In the non-affected contralateral eyes, the mean PCT was 192.5±60.6 μm (range, 61.4-365.0 μm) at baseline and 165.9±61.1 μm (range, 56.8-326.8 μm) at 6mo (P<0.001). In sectoral analysis, the mean PCT in each sector was significantly reduced in over 6mo in the BRVO-affected eyes (all P<0.001). In the non-affected contralateral eyes, the mean PCT was not significantly changed in any sector over the 6-month follow-up period (superior sector, P=0.143; temporal sector, P=0.825; inferior sector, P=0.192; and nasal sector, P=0.599). CONCLUSION: Sectoral analysis shows that the mean PCTs in all sectors are reduced significantly over 6mo in the BRVO-affected eyes, but not in the non-affected contralateral eyes.