BACKGROUND: Peritumoral lymphoid aggregates, termed Crohn's-like lymphoid reaction (CLR), are markers of an antitumor immune response, which is an important predictor of patient outcome. In this study, we investigated the prognostic utility of CLR and its relationship with nutritional status in patients with gastric cancer (GC). METHODS: The study included 170 patients who underwent curative surgery for pathological stage (pStage) II/III GC. The maximum diameters of peritumoral and normal mucosal CLR aggregates were measured, and the median peritumoral diameter (0.57 mm) was used to stratify patients into two groups (large-CLR and small-CLR). The relationships between CLR size and preoperative nutritional status (body mass index, body composition status, Onodera's prognostic nutritional index), tumor-infiltrating CD8+ T-lymphocyte count, and survival were evaluated. RESULTS: Peritumoral CLR aggregates were significantly larger than aggregates in the normal mucosa. Clinicopathological variables were not significantly different between the two patient groups; however, the large-CLR group had better cancer-specific survival (p = 0.018) and recurrence-free survival (p = 0.03) than the small-CLR group. Multivariate analysis revealed that CLR size was an independent prognostic factor for cancer-specific survival [hazard ratio (HR) 2.13, 95% confidence interval (CI) 1.3-3.56, p = 0.002] and recurrence-free survival (HR 1.96, 95% CI 1.22-3.19, p = 0.005). Nutritional status markers were significantly poorer for the small-CLR group than the large-CLR group. CD8+ T-cell tumor infiltration was positively correlated with CLR size but not with patient survival. CONCLUSIONS: CLR size correlated with patient nutritional status and prognosis and may be helpful in identifying high-risk populations of pStage II/III GC patients.