Pernicious anaemia is an autoimmune disorder where vitamin B12 deficiency is caused by autoantibodies that interfere with vitamin B12 absorption by targeting intrinsic factor or parietal cells or both. It is commonly associated with anaemia, rarely pancytopenia. Here we reported two cases of pancytopenia due to undiagnosed pernicious anaemia. First case was a 26-year-old man presented with lethargy and reduced effort tolerance, associated with postural giddiness and palpitation. Clinically, he was pale with no other findings. On blood investigations, the patient was diagnosed pancytopenia secondary to pernicious anaemia. He was treated with daily subcutaneous injection of vitamin B12 cyanocobalamin 1 mg for one week followed by weekly injection for a month and subsequently with lifelong monthly subcutaneous injection. After receiving 2 weeks of B12 replacement, his full blood count had normalized and his symptoms resolved. Second case was a 65-year-old man presented with yellowish discolouration of the eyes with lethargy. On examination, he was pale with jaundice. On blood investigations, the patient was diagnosed pancytopenia secondary to pernicious anaemia. He was started with intramuscular injection of 1000 mcg vitamin B12 replacement daily for one week followed by monthly for 6 months. After one week of B12 replacement, his full blood count had normalized. He was started on lifelong 3 monthly injections of vitamin B12 replacement and he remained symptom free. Patients with pernicious anaemia often present with general signs and symptoms which occur insidiously. It is important that early diagnosis is made to avoid harmful complications such as neuropsychiatric disorders.