ABSTRACT Recent studies describing the mutational landscape of head and neck squamous cell carcinoma (HNSCC) on a genomic scale by our group and others, including The Cancer Genome Atlas, have provided unprecedented perspective for understanding the molecular pathogenesis of HNSCC progression and response to treatment. These studies confirmed that mutations of the TP53 tumor suppressor gene were the most frequent of all somatic genomic alterations in HNSCC, alluding to the importance of the TP53 gene in suppressing the development and progression of this disease. Clinically, TP53 mutations are significantly associated with short survival time and tumor resistance to radiotherapy and chemotherapy in HNSCC patients, which makes the TP53 mutation status a potentially useful molecular factor for risk stratification and predictor of clinical response in these patients. In addition to loss of wild‐type p53 function and the dominant‐negative effect on the remaining wild‐type p53, some p53 mutants often gain oncogenic functions to promote tumorigenesis and progression. Different p53 mutants may possess different gain‐of‐function properties. Herein, we review the most up‐to‐date information about TP53 mutations available via The Cancer Genome Atlas‐based analysis of HNSCC and discuss our current understanding of the potential tumor‐suppressive role of p53, focusing on gain‐of‐function activities of p53 mutations. We also summarize our knowledge regarding the use of the TP53 mutation status as a potential evaluation or stratification biomarker for prognosis and a predictor of clinical response to radiotherapy and chemotherapy in HNSCC patients. Finally, we discuss possible strategies for targeting HNSCCs bearing TP53 mutations. J. Cell. Biochem. 117: 2682–2692, 2016. © 2016 Wiley Periodicals, Inc. In this article, we review the most up‐to‐date information about TP53 mutations available via The Cancer Genome Atlas (TCGA)‐based analysis of head and neck squamous cell carcinoma (HNSCC). We also discuss the use of the TP53 mutation status as a potential evaluation or stratification biomarker for prognosis and a predictor of clinical response to radiotherapy and chemotherapy in HNSCC patients. Finally, we summarize possible strategies for targeting HNSCCs bearing TP53 mutations.