Background: Tumor necrosis has been identified as an independent adverse prognostic factor in various human malignancies; however, its prognostic value in gastric gastrointestinal stromal tumors (gGISTs) remains uncertain. This study aimed to investigate the association between tumor necrosis and overall survival (OS) in patients with gGIST who underwent radical surgical resection. Methods: In this retrospective cohort study, clinical and pathological data from 1,463 patients with gGIST were analyzed. The association between tumor necrosis and OS was assessed using univariate analysis with log-rank tests and multivariate analysis with Cox proportional hazards regression models. Results: Tumor necrosis was observed in 238 patients (16.3%) and was significantly associated with tumor location (P=0.044), tumor size (P<0.001), mitotic count (P<0.001), and modified National Institutes of Health (NIH) risk categories (P<0.001). Multivariate analysis confirmed tumor necrosis as an independent unfavorable predictor of OS (P=0.02). Incorporating tumor necrosis into the modified NIH risk classification enabled the stratification of patients into five prognostically distinct groups (P<0.001). Conclusions: Tumor necrosis was identified as an independent adverse prognostic factor in gGIST, and its integration into the modified NIH classification improves prognostic accuracy, supporting a refined risk stratification system for enhanced clinical decision-making and patient management.