Immune thrombocytopenia (ITP) caused by infectious and non-infectious conditions has been reported in coronavirus disease 2019 (COVID-19) patients too. Here we present a 64-year-old male patient with post-COVID-19 pneumonia who presented with a gastrointestinal bleed and was found to have severe isolated thrombocytopenia (22,000/cumm) diagnosed as ITP with extensive investigations. He was treated with pulse steroid therapy and later was also given intravenous immunoglobin in view of poor response. The addition of eltrombopag also resulted in a sub-optimal response. He was also having low vitamin B12, and his bone marrow also supported the megaloblastic picture. Hence, injectable cobalamin was added to the regimen, which resulted in a sustained rise in platelet count that reached 78,000/cumm, and the patient got discharged. This shows the possible hindrance to treatment response by concomitant B12 deficiency. Vitamin B12 deficiency is not an uncommon entity and should be tested in those who show no or slow response to thrombocytopenia.