Background <p>Tumor deposits (TD) have been identified as adverse prognostic indicators in gastric cancer (GC); however, their incorporation into the TNM staging system remains controversial. This study aimed to determine the most effective approach for integrating TD into the TNM staging system to improve prognostic accuracy.</p> Methods <p>A retrospective analysis was performed on clinicopathological and follow-up data from patients who underwent radical surgery for gastric cancer (GC) at Yijishan Hospital, affiliated with Wannan Medical College, between January 2012 and December 2021. Patients were classified into TD-negative and TD-positive groups according to the presence or absence of TD in postoperative pathological reports.</p> Results <p>A total of 4,972 patients were analyzed, of whom 575 (11.56%) had TD. These patients were matched in a 1:1 ratio with 523 TD-negative patients. Several clinicopathological factors, including tumor size, T stage, N stage, neural invasion, and vascular invasion, were significantly associated with the presence of TD. Survival analysis revealed that patients with TD had significantly lower 5-year overall survival (OS) rates than those without TD across all TNM stage subgroups (I–II, IIIa, IIIb, and IIIc) (<i>P</i> &lt; 0.05). The 5-year OS rates of patients with TD in stages I–II, IIIa, IIIb, and IIIc were comparable to those of TD-negative patients in stages IIIa, IIIc, IIIc, and IV, respectively (<i>P</i> &gt; 0.05). The proposed staging system incorporating TD demonstrated the highest χ² value (181.658), the highest C-index (0.634), and the lowest − 2 log-likelihood (8427.456), indicating improved prognostic stratification.</p> Conclusion <p>TD represent independent prognostic factors in GC, distinct from the T, N, and M categories, and should be incorporated into the TNM staging system.</p>