Purpose: This study aimed to ascertain cytokine concentrations in patients with center macular edema (CME) due to branch retinal vein occlusion (BRVO) before and during the period of treatment with intravitreal injection of conbercept (IVC) and to determine the relationship between these concentrations and disease activity. Materials and methods: The Bio-Plex ® 200 System and the Bio-Plex TM Human Cytokine Standard 27-Plex, Group I (Bio-Rad, Hercules, California, USA) were used to detect cytokine concentrations in aqueous humour. Experimental aqueous humour samples were collected from 22 patients with CME due to BRVO when IVC was administered at baseline and at 1 month, and control aqueous samples were collected by limbal paracentesis from 16 patients undergoing routine cataract surgery. Results: Significantly higher concentrations of vascular endothelial growth factor (VEGF), interleukin 6 (IL-6), IL-8, interferon gamma-induced protein 10 (IP-10), and monocyte chemoattractant protein-1 (MCP-1) were found in the BRVO group than in the control group. In the BRVO group, VEGF levels were significantly lower one month after IVC than at baseline. However, the other cytokines did not significantly change during IVC treatment. The decreases in VEGF levels were closely related to the decreases in central macular thickness (CMT) and the increases in best-corrected visual acuity (BCVA). Conclusions: Many factors, such as angiogenic, inflammatory and growth factors, contribute to the pathogenesis of CME due to BRVO. IVC had no significant effect on cytokines other than VEGF in patients with CME due to BRVO. The changes in BCVA and CMT were associated with VEGF levels after IVC treatment.