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HER2-low expression has recently gained considerable attention as an actionable biomarker in gastric cancer (GC). However, clinical implications of HER2-low expression in GC remains uncertain, which limited its precise management in the era of antibody‒drug conjugates. This study aims to describe the clinicopathological features and its value in predicting outcomes for GC patients. We performed a retrospective study of 994 patients (248 with HER2-low expression and 746 with HER2-zero expression) from January 2018 to December 2023. Each cohort was further divided into non-metastatic (M0) and metastatic (M1) subgroups. Clinicopathological features and survival outcomes were collected and compared between HER2-low and HER2-zero GC. Kaplan–Meier analysis and Multivariable Cox regression analyses were utilized to confirm the prognostic value. Furthermore, a nomogram was established to predict overall survival (OS) rates at 1, 2, and 3 years. The Concordance index (C-index), time-dependent receiver operating characteristic (ROC) curves and calibration curves were utilized to assess the discrimination and reliability of the Model. Significant differences were observed in age (≥ 60 years: 65.3% vs. 55.2%, P = 0.005) and ethnicity (Hui ethnicity:12.5% vs.19.4%, P = 0.001) between the HER2-low and HER2-zero GC. HER2-low GC had lower T stage than HER2-zero GC, with T3 stage (21.8% vs. 12.5%) and T4 stage (58.1% vs.65.4%) P < 0.05. HER2-low status was identified as an independent prognostic factor associated with worse survival outcomes, particularly in patients with GC at M0 stage (HR 1.420; 95% CI 1.058–1.907). The nomogram prediction model was constructed by including these factors at M0 stage. The C-index, AUC value and calibration curves demonstrated that the nomogram performed well in predicting OS at 1, 2, and 3 years. The findings from the present study demonstrated that patients with HER2-low GC exhibited distinct pathological characteristics and had a worse prognosis. Further research is warranted to refine future diagnostic and treatment strategies for this subgroup.