To evaluate the effectiveness of coronoidectomy to prevent trismus in patients undergoing primary surgery for oral cancer. Patients who underwent primary surgery for oral gingivo-buccal cancers were analysed. Group 1 (G1) consists of patients who underwent coronoidectomy during the primary ablative procedure and group 2 (G2) who underwent standard ablative surgery without coronoidectomy. Post-treatment maximum interincisor opening was compared between the two groups. Sixty-four patients were included, 31 in G1 and 33 patients in G2. Overall, 81% had reduction in mouth opening at the time of evaluation. The post-treatment mean mouth opening was 28.81 ± 8.2 and 22.30 ± 10.9 (p = .01) in G1 and G2, respectively. Amongst factors predisposing to trismus, patients with oral submucous fibrosis (p = .008) had reconstruction with microvascular free flap (p = .007), without post-operative radiotherapy (p = .01) and good patient compliance (p = .003) had significant benefit with simultaneous coronoidectomy. In the sub-group analysis in patients without OSMF and PORT, the mean reduction in mouth opening was significantly better in G1 (p = .04). Prophylactic coronoidectomy done at the time of primary surgery showed significant reduction in post-surgical trismus.