CDKN2A (: p16) disruption is reported as a frequent event in head and neck squamous cell carcinomas that confers poor prognosis. We investigated the frequency of different potential mechanisms of CDKN2A inactivation in oral tongue squamous cell carcinomas (OTSCC) and their impact on patient outcome. From a cohort of 153 OTSCC patients, 131 formalin fixed paraffin embedded blocks of pre-treatment primary tumours were suitable for further molecular analysis. We assessed CDKN2A (p16) levels by immunohistochemistry (IHC), promoter methylation status by methylation-sensitive high resolution melting, mutation status by Sanger sequencing, gene copy number variation by fluorescence in situ hybridisation, and correlated these with patient outcome. We found that the majority of OTSCC did not overexpress p16 (110/116, 95%), assessed by IHC. The frequency of CDKN2A mutations was 20% (21/103), homozygous loss was 7% (7/97), hemizygous loss 31% (30/97), and promoter methylation was 18% (20/113). We found no evidence of these mechanisms in 24/106 (23%) p16 IHC negative tumours. No significant correlation was identified between any potential mechanism of CDKN2A inactivation and clinical features, including smoking status and age. There was a non-significant trend for worse overall survival for p16 IHC negative patients versus positive patients (HR = 1.81, 95% CI = 0.44–7.47, p = 0.40). No relationship was found between mechanisms of CDKN2A disruption and patient outcome. In conclusion, we demonstrate that CDKN2A alteration is a frequent event in OTSCC tumourigenesis. However, no correlation was identified between different potential mechanisms of CDKN2A disruption and clinical characteristics or patient outcome. WHATʼS NEW?: Despite early detection and treatment, oral tongue squamous cell carcinoma (OTSCC) often is associated with poor prognosis. Among certain cancers of the head and neck, poor prognosis appears to be linked to CDNK2A (p16) disruption. To determine whether such a link exists in OTSCC, this study explored potential differential mechanisms of CDNK2A inactivation among OTSCC patients. CDKN2A alteration was found to be a recurrent event in OTSCC tumorigenesis. The different mechanisms of disruption, however, had no impact on OTSCC clinical characteristics or patient outcome.