Tumor-infiltrating neutrophil (TIN) has been reported to be an independent predictor in multiple tumors, but its role in the development of adenocarcinoma of the esophagogastric junction (AEG) remains unclear. We conducted immunohistochemistry (IHC) to detect the expression of TIN in 113 consecutive patients with primary AEG. The prognostic value and its relationship with clinicopathological characteristics and Ki-67 (a proliferation-associated antigen) expression were analyzed. High level of TIN was related to poor outcome in AEG patients with a hazard ratio (HR) of 3.93 (95% confidence interval (CI) = 2.14-7.19, p < 0.001) in univariate analysis and a HR of 3.44 (95% CI = 1.85-6.37, p < 0.001) in multivariate analysis. In addition, TIN was positively correlated with Ki-67 expression (p = 0.008). Our study found that TIN expression was an independent unfavorable predictor in AEG. Furthermore, the relationship between TIN and Ki-67 indicated that TIN was associated with tumor proliferation, which might provide a potential mechanism for why TIN was related to poor outcome in AEG.