Gastric cancer, a prevalent malignancy, often presents challenges due to its low early diagnosis rate and poor prognosis. This study aims to establish a prognostic model composed of genes from the CLEC family, aiming to predict the prognosis of gastric cancer patients effectively. Data Collection: mRNA expression matrices and clinical data were downloaded from the TCGA, GEO, and GTEx databases. Differential analysis, univariate Cox analysis, lasso regression analysis, and multivariate Cox analysis were conducted to identify three genes associated with the prognosis of the CLEC family for building a prognostic model. Prognostic Model Construction: A prognostic model comprising these three genes was constructed. The prognostic value was evaluated using Kaplan-Meier plots, time-dependent receiver operating characteristic curves, multivariable Cox regression analysis incorporating clinical information, and a nomogram. The predictive value of the three-gene signature was further validated using the GSE84437 dataset. Immune and Functional Analyses: Differences in immune status and signaling pathways between different risk groups were assessed through analyses of the tumor microenvironment, immune cell infiltration, immune function, and gene set enrichment. Through tumor mutation analysis, the molecular mechanisms of tumors were revealed. Finally, chemotherapy-sensitivity drugs were identified through drug analysis. Results revealed CD93, CLEC3A, and VCAN as three CLEC family genes associated with prognosis. Multivariable Cox regression analysis demonstrated that these three CLEC family genes were independent prognostic factors for overall survival in gastric cancer patients. Additionally, we constructed a prognostic nomogram that incorporated risk score, age, grade, and stage. Based on TCGA/GSE84437 data, calibration plots demonstrated its predictive solid performance. Furthermore, immune-related analyses and drug sensitivity assessments suggested a close association between the three-gene model and immune cell infiltration, indicating their potential as predictive indicators for chemotherapy sensitivity. We have identified a CLEC family gene model consisting of three genes associated with the prognosis of gastric cancer. This provides a basis for personalized prevention and treatment strategies.