Isoniazid (INH) is one of the first line drugs for category I antitubercular therapy (ATT). The most notable adverse effect due to INH is hepatitis. Acute pancreatitis is rarely caused by medications with an estimated incidence of 0.1–2%. Isoniazid is a rare cause of acute pancreatitis. We here report a case of patient diagnosed with tubercular meningoencephalitis was started ATT consisting of RIMACTAZID (Rifampicin + Isoniazid), Pyrazinamide, Ethambutol and Streptomycin along with prednisolone and within a weekthe patient developed pain abdomen with diarrhoea. Investigations showed abnormal pancreatic function and imaging suggested acute pancreatitis. ATT were temporarily stopped and 10 days later pancreatic enzymes returned to normal values.  Suspected Adverse Drug Reaction was reported. The causality of isoniazid was found to be ‘probable’ by the WHO–UMC causality scale and causal relationships of other drugs were evaluated and found to be ‘possible’.