Paediatric cases of acute acalculous cholecystitis (AAC) are due to infectious diseases or immune mediated disorders. Hereby, we present a case of 6 months old infant who presented with excessive crying with irritability and tenderness over right hypochondrium region with a palpable liver. Investigations revealed   AAC and anaemia. In the work-up of anaemia, vitamin B12 deficiency was diagnosed and after giving treatment with vitamin B12, anaemia resolved as well as AAC. Through this case report we intent to emphasize the possibility of vitamin B12 deficiency presenting as AAC.