61-year old male patient was admitted to the hospital with clinical picture of hemolytic anemia with hemoglobinuria. Patient was suspected to have Infectious Mononucleosis (IM) with Auto Immune Hemolytic Anemia (AIHA). DAT was positive with anti-C3d specificity. Donath Landsteiner (DL) test was positive; confirming Paroxysmal Cold Hemoglobinuria (PCH). The final diagnosis was IM with PCH. Patient was managed conservatively and discharged after seven days. DL test specifically detects a biphasic autoantibody (IgG type) that binds to RBCs at cold temperatures, and fixes complement on the RBC membrane. However RBCs are only lysed upon warming to 37C when complement cascade proceeds to completion.