Passenger lymphocyte syndrome (PLS) is a subtype of graft-versus-host disease caused by the production of antibodies by transferred donor B-lymphocytes against red blood cells (RBCs) of the recipient. A 64-year-old male diagnosed with stage five chronic kidney disease underwent bidirectional ABO-mismatched kidney transplantation. The blood groups of the recipient and the donor were A+ and B+, respectively. After transplantation, hemoglobin (Hb) levels were eventually reduced to 6.3 g/dL on postoperative day (POD) 25. Elevated lactate dehydrogenase levels and positive direct antiglobulin test results indicated immune-mediated hemolysis as a possible cause of anemia. After switching RBC transfusion from type-A to type-O and conducting plasma exchange four times, on POD 35, Hb levels of the patient recovered up to 9.1 g/dL, and the patient was discharged from the hospital without complications. To the best of our knowledge, PLS in a bidirectional ABO-mismatched solid organ transplantation has been reported once in India, and this is the first case to be reported in Korea.