This study aims to ascertain whether cytokines in the aqueous humor can predict macular edema (ME) in diabetic patients following uncomplicated phacoemulsification cataract surgery. Undiluted aqueous humor samples were obtained from 136 consecutive type 2 diabetic patients who underwent cataract surgery. The concentrations of 27 cytokines were measured in aqueous humor using the multiplex bead immunoassay. At the final follow-up examination, 116 patients completed 4 weeks of follow-up, and the incidence of macular edema was 29.31% (34 patients) 4 weeks after cataract surgery. Compared to the ME (-) patients, the concentrations of interleukin-1β (IL-1β) (P < 0.001), IL-6 (P < 0.001), IL-8 (P < 0.001), interferon-induced protein-10 (IP-10) (P = 0.003), monocyte chemotactic protein-1 (MCP-1) (P < 0.001), and vascular endothelial growth factor (VEGF) (P < 0.001) in the ME (+) patients were significantly higher. In addition, the aqueous levels of IL-1β (r = 0.288), IL-6 (r = 0.345), IL-8 (r = 0.256), IP-10 (r = 0.377), MCP-1 (r = 0.423), and VEGF (r = 0.279) were positively correlated with the postoperative foveal center point thickness (FCPT). However, the aqueous levels of IL-10 (P = 0.003) and IL-12 (P = 0.017) were significantly lower in patients with ME. These results suggest IL-1β, IL-6, IL-8, IL-10, IL-12, IP-10, MCP-1, and VEGF may be potential predictors of postoperative macular thickness in patients with diabetes following uncomplicated phacoemulsification cataract surgery.