Immunotherapy has revolutionized cancer treatment, yet many patients show non-sensitivity. Here, we collected treatment-naïve samples from 190 esophageal squamous cell carcinoma (ESCC) patients undergoing anti-programmed death 1 (PD1) immunotherapy for proteome, phosphoproteome, and immunohistochemistry (IHC) analysis. Proteome-based stratification of ESCC identifies three proteomic subtypes (G-I-G-III) related to immunotherapy response and different molecular features, revealing that patients with high mitochondrial complex I protein expression show sensitivity to anti-PD1 immunotherapy. High mitochondrial complex I protein expression of ESCC cells or patient-derived organoids increases sensitivity to CD8 + T cell-mediated killing in the co-culture systems. Phosphoproteomic data analysis reveals YAP1 activation impairs immunotherapy efficacy. Inhibiting YAP1 or increasing mitochondrial complex I levels bolsters immunotherapy effectiveness in ESCC allograft tumors. Finally, we develop a highly accurate predictive model (AUC ≥ 0.90) by the signatures of mitochondrial complex I-mediated anti-tumor immune response and validate it in independent cohorts. This study provides a rich resource for investigating the mechanisms and indicators of immunotherapy in ESCC.