The role and effectiveness of non-vascularised bone grafts (NVBG) in reconstructing post-oncologic segmental mandibular defects remain inconsistent and debated, particularly in the setting of a compromised recipient bed often affected by prior radiation therapy and significant soft tissue loss. This systematic review and meta-analysis aimed to assess the outcomes of NVBGs for segmental mandibular defects resulting from oral cancer resection. A comprehensive electronic search of literature up to June 30, 2025, identified relevant studies. Inclusion criteria followed PICOT - NVBG reconstruction for segmental mandibular defects after oral cancer resection, as compared to vascularised free flaps or none, yield optimum results in terms of graft integration, complications, function, and aesthetics. The risk of bias in individual studies was assessed using the Newcastle Ottawa Scale. A quantitative synthesis was performed for graft failure, being defined as clinical or radiographic non-union, between irradiated and non-irradiated NVBG to estimate the overall effect size and assess between-study variability. Eleven studies involving 202 NVBGs were included. The overall graft uptake derived from all eligible studies was noted in 160 patients with a descriptive success rate of 80.4%. A total of 4 studies, which compared irradiated with the non-irradiated groups, were included in the meta-analysis, showing a pooled odds ratio of 2.83 (95% CI: 0.75 to 10.61), indicating no statistically significant difference for graft failure (P = 0.12). The obtained results reflect a trend towards higher failure in irradiated patients; however, not statistically significant, based on very low-quality evidence with a wide confidence interval.