This study investigated the effects of ACE inhibition on Head and Neck Squamous Cell Carcinoma (HNSCC), tumor progression, and the relation of ACE2, AGTR1, ACE, and MAS1 expression with HNSCC patient` survival. ACE inhibitor (Captopril) treatment was applied into Swiss male mice. ACE2, AGTR1, ACE, and MAS1 expression levels were analyzed in HNSCC tumor tissues from The Cancer Genome Atlas (TCGA) database. ACE inhibition reduced cell viability, proliferation, migration, and invasion, increased ROS levels, and induced apoptosis in SCC9 cells. Neoplastic angiogenesis was suppressed by ACE inhibition in the CAM assay. ACE inhibition also reduced the incidence of severe dysplasia/carcinoma in the histological analysis. TCGA data revealed that lower ACE2 levels were associated with poorer survival outcomes, while increased AGTR1 expression correlated with a higher risk of death in HPV-negative patients. ACE upregulation and higher MAS1 expression were observed in HNSCC tumor tissues. ACE inhibition demonstrated anti-cancer effects in HNSCC cells and suppressed neoplastic angiogenesis. It also reduced histological aggressiveness and showed potential predictive value for ACE2 and AGTR1 expression levels in HNSCC. These findings suggest the therapeutic potential of ACE inhibitors in HNSCC treatment, requiring further investigation and validation in clinical settings.