Background: Buccal mucosa squamous cell carcinoma poses a significant public health burden in Bangladesh, with over 7,000 new cases annually. The accuracy of MDCT in preoperative staging and its correlation with histopathological TNM staging remains unclear. Therefore, the purpose of this study is to evaluate the correlation between MDCT findings and histopathological TNM staging in patients with buccal malignancy. Methods: This cross-sectional diagnostic accuracy study at the Departments of Radiology and Imaging, Otolaryngology and Head–Neck Surgery, and Pathology, Sylhet MAG Osmani Medical College and Hospital (March 2020–February 2022) included 65 histopathologically confirmed buccal malignancy patients who underwent punch biopsy, contrast-enhanced MDCT, and surgical resection for TNM staging. MDCT findings were compared with histopathology, data were analyzed using SPSS v23, and ethical approval with informed consent was obtained. Results: Among 65 patients (mean age 52.8 ± 11.1 years; 67.7% male), MDCT detected retromolar trigone involvement in 42 (64.6%) and masticator space in 28 (43.1%), with bone involvement in 16 (24.7%) and ipsilateral lymph nodes in 50 (77.0%). Histopathology showed Stage IVB in 27 (41.5%) and IVA in 20 (30.8%). Radiological staging concordance was highest for Stage IVB (96.3%), and MDCT demonstrated high sensitivity (75–96.3%), specificity (94.5–98.2%), and accuracy (>92%) across stages. Conclusion: MDCT reliably correlates with histopathological TNM staging and accurately guides preoperative assessment in buccal malignancy.