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Cancer-associated fibroblasts (CAFs) orchestrate immune-excluded tumor microenvironment (TME), but the CAF heterogeneity remains incompletely understood in gastric cancer (GC). In this study, we integrated multicohort single-cell RNA sequencing (scRNA-seq), spatial transcriptomics, and bulk transcriptomic data to construct a comprehensive atlas of the GC TME. Unsupervised clustering identified eight transcriptionally distinct CAF subpopulations, among which CTHRC1+ CAFs were selectively enriched in tumors and showed the strongest association with T cell exclusion. Pseudotemporal trajectory analysis, gene regulatory network inference, and cell-cell communication analysis revealed that basic helix-loop-helix family member e41 (BHLHE41) serves as a key transcription factor driving CTHRC1+ CAF differentiation, whereas spatial analyses demonstrated these fibroblasts contribute to fibrotic niches at the tumor-stroma interface through macrophage migration inhibitory factor (MIF)-mediated signaling. Finally, we developed and validated a CTHRC1+ cancer-associated fibroblast-related risk signature (CRS) that accurately predicts immunotherapy response across independent cohorts. These findings establish CTHRC1+ CAFs as a critical stromal determinant of immune exclusion in GC, suggesting that targeting the CTHRC1+ CAF-MIF axis or applying CRS-guided patient stratification may enhance immunotherapy efficacy.