Introduction: Margin status is a key prognostic factor in oral cavity squamous cell carcinoma (OSCC), yet the contributions of tumour biology and anatomical constraints to margin involvement remain unclear. This study evaluated the relationship between margin burden, anatomical distribution, and survival outcomes. Methods: A retrospective cohort of 186 patients with OSCC treated 2012–2024 was studied. Demographic, clinicopathological, and survival data were collected. Margin status was categorised by clearance (>5 mm, 1–4 mm, <1 mm), number of involved or close margins, and anatomical site (radial vs deep). Associations with pathological variables and overall survival were analysed. Results: The cohort comprised 186 patients (53.8% male); pathological staging was 57 pT1, 50 pT2, 20 pT3, and 57 pT4a. Clear margins were achieved in 57.5%, with 28.5% close and 11.3% involved. Multiple margin involvement occurred in 36.5% close and 28.6% involved cases. Involved/close margin location varied significantly by subsite (p < 0.001): deep margin involvement was most frequent in tongue tumours (71%), whereas radial involvement predominated in mandibular (31%), floor of mouth (22%), and maxillary (19%) subsites. Advanced stage (pT4a) and perineural invasion (PNI) were significantly associated with close and involved margins (p = 0.009 and 0.035). Close radial margins were associated with pT4a (p = 0.004) and floor of mouth subsite (p = 0.002); close deep and involved margins were associated with PNI (p = 0.034 and 0.021). On survival analysis, involved margins (p < 0.001), floor of mouth subsite (p = 0.002), tumour differentiation (p = 0.004–0.001), and increasing tumour size predicted poorer overall survival. Conclusion: Margin status in OSCC reflects both tumour biology and anatomical constraints. Advanced stage and PNI predispose to margin involvement; margin location is subsite-dependent. Involved margins are prognostically significant, but margin multiplicity is not.