Aim: Evaluation of adverse drug reactions in patients of diabetes mellitus on 1st line Antitubercular treatment. Methods: Patients presenting to the Medicine OPD (Diabetic clinic), and Respiratory medicine OPD, KGMU, on specified days of the week diagnosed to be diabetes mellitus with tuberculosis was screened based on selection criteria. Written informed consent was taken from patients. Demographic details of the participants were recorded in semistructured proforma. The overall description of the adverse drug effect was done for the selected patients. Seriousness of adverse drug effects were evaluated. Assessment of the severity of adverse drug effects were done. Causality assessment of ADRs was assessed by the WHO-UMC causality assessment system and Naranjo’s causality assessment scale. The severity of ADRs was assessed by Hartwig’s Severity Assessment and scale.