BACKGROUND A ≥5mm tumour free excision margin (TFEM) has traditionally been regarded as a clear in oral cavity squamous cell carcinoma (OCSCC). Previous studies group the TFEM into categories: transected, very close <1mm, close 1-4.9mm and clear ≥5mm. This study aimed to evaluate the effect of the TFEM on locoregional recurrence, overall mortality and cancer-specific mortality in OCSCC, and whether there was a specific margin cut-off that negatively impacted these outcomes. METHODS All patients with OCSCC undergoing major head and neck surgery between 2009-2021 at Hutt Hospital were identified from our Head and Neck Database. Primary outcome measures were odds of recurrence, overall mortality and cancer-specific mortality at 1, 2 and 5years. Multivariate analysis was performed adjusting for T-stage, differentiation, perineural invasion, lymphovascular invasion, metastatic disease to the neck, comorbidities and adjuvant radiotherapy. RESULTS The odds of locoregional recurrence within 1 year was reduced by 10%(p=0.98), 2 years by 14%(p=0.011) and 5 years by 13%(p=0.017) for every mm increase in TFEM. The odds of all-cause mortality within 1 year was reduced by 20%(p=0.049), 2 years by 16%(p=0.004), and 5 years by 15%(p=0.003) for every mm increase in TFEM. The odds of cancer-specific mortality within 1 year was reduced by 26%(p=0.003), 2 years by 20.5%(p=0.002) and 5 years by 18%(p=0.005) for every mm increase in TFEM. On multivariate analysis, these results remained significant. There was no margin cut-off that negatively impacted these outcomes. CONCLUSION Increased TFEM are associated with reduced odds of loco-regional recurrence, all-cause mortality and cancer-specific mortality within 1, 2 and 5 years in OCSCC.