The EGFR-targeting antibody cetuximab (CTX) combined with radiotherapy is the only targeted therapy that has been proven effective for the treatment of locally advanced head and neck squamous cell carcinoma (LA-HNSCC). Recurrence arises in 50% of patients with HNSCC in the years following treatment. In clinicopathological practice, it is difficult to assign patients to classes of risk because no reliable biomarkers are available to predict the outcome of HPV-unrelated HNSCC. In the present study, we investigated the role of Caveolin-1 (Cav1) in the sensitivity of HNSCC cell lines to CTX-radiotherapy that might predict HNSCC relapse. Ctrl- and Cav-1-overexpressing HNSCC cell lines were exposed to solvent, CTX, or irradiation, or exposed to CTX before irradiation. Growth, clonogenicity, cell cycle progression, apoptosis, metabolism and signaling pathways were analyzed. Cav1 expression was analyzed in 173 tumor samples and correlated to locoregional recurrence and overall survival. We showed that Cav1-overexpressing cells demonstrate better survival capacities and remain proliferative and motile when exposed to CTX-radiotherapy. Resistance is mediated by the Cav1/EREG/YAP axis. Patients whose tumors overexpressed Cav1 experienced regional recurrence a few years after adjuvant radiotherapy ± chemotherapy. Together, our observations suggest that a high expression of Cav1 might be predictive of locoregional relapse of LA-HNSCC.