Aim: To compare biodosimetry in head and neck cancer patients undergoing concurrent chemoradiotherapy versus accelerated fractionation radiotherapy using the dicentric chromosomal aberration assay. Methods: The study was conducted at Maulana Azad Medical College and Lok Nayak Hospital, New Delhi, spanning 12 months, focusing on histopathologically confirmed cases of head and neck cancers. Patients were randomly assigned in a 1:1 ratio to either the CTRT or AFRT treatment groups. Cytogenetic analysis was performed on all 32 patients. Dicentric chromosome yield was measured in blood samples collected before treatment initiation and at various points during radiotherapy (baseline, 7th, and 13th fractions), with assessments conducted one hour post-radiotherapy each time. Results: In the chemoradiotherapy group, the mean dicentric chromosome yield per cm² exceeded that of the accelerated radiotherapy group by 7.52% and 16.20% on days 7 and 13 of treatment, respectively. Additionally, the CTRT arm showed a significantly higher overall response rate (p=0.024). Conclusion: Our data confirm that there is a benefit of adding chemotherapy with radiotherapy when compared with accelerated radiotherapy in terms of the number of dicentric chromosomal aberrations.