Background/Aim: This study evaluated the associations between bone invasion of gingival squamous cell carcinoma (SCC) and clinicopathological manifestations, and aimed to determine whether bone invasion is an independent prognostic factor in gingival SCC. Patients and Methods: The study was a retrospective review of 78 patients with gingival SCC who underwent surgery with curative intent. The level of bone invasion was pathologically categorized as medullary, cortical or no bone invasion. Results: Cortical and medullary bone invasion was present in 29 and 22 patients, respectively. There was a significant association between medullary bone invasion and tumor size (p=0.017), pathological N classification (p<0.001), differentiation (p=0.017) and lymphovascular invasion (p=0.007). Medullary bone invasion and lymphovascular invasion were independent predictors of reduced overall survival (p=0.015, 0.048); medullary bone invasion was also an independent predictor of reduced disease-specific survival (p=0.018). Conclusion: Pathologically-proven medullary bone invasion and lymphovascular invasion were found to be key prognostic factors in gingival SCC. The results suggest that it is necessary to consider adjuvant therapy in patients with medullary bone invasion.