Deficiency of vitamin B12 and/or folic acid as a cause of pyrexia, though known, is rarely reported in literature. We aimed to report a case in a 51 year old woman, who presented with fever and pancytopenia and was diagnosed to have megaloblastic anemia secondary to vitamin B12 and folate deficiency. The pyrexia subsided following the intramuscular injection of vitamin B12 and oral folic acid administration. All the other infective, inflammatory/autoimmune, endocrine causes of pyrexia were excluded by appropriate investigations. Therefore, we suggest that all physicians be aware of megaloblastic anemia as a treatable cause of pyrexia in order to avoid unnecessary costly investigations and antibiotic usage.