Cold agglutinin disease (CAD) is a subgroup of autoimmune hemolytic anemia (AIHA). This is usually associated with cold reactive autoantibodies. Acute form of CAD is attributed to infectious or autoimmune disease and chronic form to lymphoproliferative disease. In this paper, we report a case of secondary CAD due to Mycoplasma pneumonia in a 34 year old female patient. Cold antibody test and direct coombs’ test were positive. The patient was treated accordingly and get relieved from the symptoms. The specific problems that occur in the blood bank or laboratory due to cold agglutinins need to be kept in mind for the accurate diagnosis and treatment of the patient.