OBJECTIVE: Identifying the drive genes and inhibiting their significant signals were persistently the main concepts in cancer treatment. However, for oral cavity squamous cell carcinoma (OCSCC), the most influential genes for overall survival (OS) remain unclear. METHODS: A total of 120 OCSCC patients with corresponding pathologic specimens were collected in Taiwan. Whole-exome sequencing was done and the prognostic impact of each gene was analyzed. TCGA database was used to validate. RESULTS: The incidences of caspase-8 mutation were 22.1% and 10.9% in the Taiwan and TCGA cohort, respectively. In the Taiwan cohort, caspase-8 mutation was the most significant independent for OS with an adjusted hazard ratio (HR) ([95% CI]: 3.83 [1.84-7.99]). It was validated by the TCGA database (HR [95% CI]: 1.51 [1.00-2.29]). The 5-year OSs of the patients with or without caspase-8 mutation were 38.1% vs. 75.3% (p < 0.001) (HR [95% CI]: 3.264 [1.645-6.438]) in the Taiwan cohort, and 26.1% vs. 49.0% (p = 0.048) (1.513 [1.001-2.288]) in the TCGA cohorts, respectively. Caspase-8 mutation was also individually associated with poor prognosis for TNM stage I/II/III/IV, respectively. CASP8 R127* and R494*, defined as pathogenic mutations in ClinVar, were presented in both cohorts. CONCLUSIONS: Caspase-8 mutation was the most significant genetic alteration impacting prognosis.