Background: The increasing incidence of oral cavity squamous cell carcinoma (OSCC) is challenging the capacity to treat patients efficiently. The aim of this study was to evaluate the impact of time to treatment initiation (TTI) on overall survival (OS) and recurrence free survival (RFS) for patients with primary OSCC. Material and methods: All patients with primary OSCC treated with curative intent at Rigshospitalet in the period 2000–2014 with known date of diagnosis and treatment initiation were included. Correlation analyses between TTI and Charlson comorbidity index (CCI), UICC stage, and year of diagnosis were performed in addition to uni- and multivariate Cox proportional hazard regression analyses. Further, interaction analysis of TTI and UICC stage were conducted. Results: Eight hundred and sixty-two patients (64% men) with a median age at diagnosis of 62 years (range: 28–95 years) were included. The median TTI was 31 days (range: 2–137 days). Correlation analyses showed correlations between TTI and CCI, TTI and UICC stage, and TTI and year of diagnosis (rho = −0.10, p-value = <.01; rho = 0.16, p-value = <.001; rho = −0.47 p-value = <.001). Univariate analyses showed a statistically significant increase in hazard ratio for both OS and RFS with a five-day increase in TTI (HR = 1.05, 95%CI: 1.02–1.07 and HR = 1.04, 95%CI: 1.02–1.07). However, when adjusting for age, sex, smoking, UICC stage, tumor sublocation, CCI, and year of diagnosis in a multivariate analysis, the increase in HR with TTI was not statistically significant. There was no statistically significant interaction between TTI and UICC stage. Conclusion: Survival of OSCC patients decreased with increasing TTI, yet not statistically significant in multivariate analysis. There was no difference in the effect of TTI between patients diagnosed in low or advanced stages.