Objective：To investigate the expression of C - type lectin 5A（CLEC5A）in gastric cancer tissues and explore its relationship with tumor-infiltrating immune cells（TILs）as well as its prognostic impact on gastric cancer patients. Methods：Based on The Cancer Genome Atlas（TCGA）database，gastric tumor samples were divided into CLEC5A mRNA high - expression and low - expression groups according to RNA sequencing data，and the association between CLEC5A mRNA expression and prognosis in gastric cancer was analyzed. Tissue microarrays from 145 gastric cancer patients（101 males and 44 females，mean age 60.6±11.2 years） who underwent surgery between March 2004 and December 2009 in the Affiliated Hospital of Nantong University Biobank were collected，with 36 non-cancerous gastric mucosal tissues as controls. Immunohistochemistry（IHC）was performed to evaluate CLEC5A protein expression and its association with clinical characteristics and prognosis. TIMER 2.0 and CIBERSORT databases were applied to evaluate the correlation between CLEC5A mRNA expression and immune infiltration levels of TILs. Multiplex immunohistochemistry（mIHC）was employed to detect immune cell distribution in the tumor microenvironment and validate the bioinformatics analysis results. Results：CLEC5A mRNA expression levels were significantly higher in gastric cancer tissues compared to normal gastric mucosa. IHC results showed that CLEC5A was expressed in both tumor cells and stromal lymphocytes，with significantly higher expression in gastric cancer tissues（27/36，75%）than in normal gastric mucosa（13/36，36.1%，P ＜ 0.05）. High CLEC5A expression was associated with better patient prognosis. Multivariate analysis indicated that low CLEC5A expression and advanced TNM stage were independent risk factors for poor prognosis in gastric cancer patients. Both bioinformatics analysis and mIHC validation demonstrated that CLEC5A expression levels were positively correlated with TIL infiltration，and the high CLEC5A expression group exhibited significantly increased infiltration of CD4 + T cells，CD8 + T cells，CD45RO+ cells，FOXP3 + T cells，PD1 + cells and PDL1 + cells compared to the low -expression group（all P ＜ 0.05）. Conclusion：CLEC5A may participate in gastric cancer progression by regulating TIL infiltration，and its high expression suggests better prognosis，potentially serving as a novel therapeutic target for gastric cancer immunotherapy.