Metformin is a commonly used first-line oral hypoglycemic agent for type 2 diabetes. Metformin associated lactic acidosis (MALA) is an extremely rare event with an estimated incidence of 0.03–0.06 per 1000 patient-years and a mortality rate of up to 50%. We report successful perioperative management of a 63-year-old man who developed MALA during his postoperative period following off-pump coronary artery bypass graft (OPCABG) surgery. MALA is a rare complication associated with metformin and is a diagnosis of exclusion. It should be considered during the perioperative period if there is suspicion of metformin accumulation. It is associated with a high mortality rate; hence, prompt recognition.