Background: WHO statistics for 2015 give an estimated incidence figure of 2.2 million cases of TB for India out of a global incidence of 9 million thus making India accountable for almost one-third of the global TB burden. The firstline antitubercular drugs include H (Isoniazid), R (Rifampicin), Z (Pyrazinamide), E (Ethambutol) and S (Streptomycin). The treatment of tuberculosis being of longer duration being a multidrug regime and of longer duration gets associated with various adverse effects. Objective: The study aimed to determine the incidence and pattern of adverse drug reactions (ADRs) of anti-tubercular drugs in tuberculosis patients treated under DOTS at tertiary care hospital of Northern India. Material and Method: A total of 115 patients were monitored for the period of 12 months. The diagnosis of tuberculosis was confirmed by sputum smear prior to enrolment. Before the patients were started on DOTS regimen, they were submitted to some pretreatment investigation and then they have been followed up to look for any adverse effects which have been recorded onto the CDSCO suspected adverse drug reaction reporting form. Results: Out of 115 patients, 58.26% i.e. 67 patients developed ADR. If we compare what percentage each age group contributed to total pool of ADR, we observe that age group 41-50 constituted (29.85%), 31-40 (22.39%); 18-30(17.91%) of the population (n=67) who developed ADR. Incidence of ADRs in category I was 57.6% while 60% in category II. Incidence of ADR in pulmonary cases came out as 57.69% while it was 56.75% in extrapulmonary cases. INTRODUCTION: Undoubtedly modern drugs have increased life expectancy and improved quality of life for millions of people. However, despite all these benefits, evidence continues to suggest that adverse reactions to medicines are common, though often preventable, cause illness, disability and even death.