Radioresistance is a major hurdle in the treatment of head and neck squamous cell carcinoma (HNSCC). Here we report a novel role for statin-based treatment of HNSCCs as an actionable and safe adjuvant to radiotherapy. Proteomic profiling and comparison of radiosensitive and radioresistant HNSCCs revealed differential regulation of the mevalonate biosynthetic pathway. Consistent with this finding, inhibition of the mevalonate pathway by pitavastatin (and other related statins) sensitized SQ20B cells to ionizing radiation (IR) and reduced their clonogenic potential. In an effort to uncover the mechanism behind this statin-mediated sensitization, we analyzed prenylation of several important cellular targets upon combined IR-statin treatment. Overall, this study reinforces the view that the mevalonate pathway is a promsing novel therapeutic target in radioresistant HSNCCs.