Herein, we report a case of post-transfusion purpura after the reversal of anticoagulation for surgical purposes in a 66-year old ethnic Asian man who was undergoing long-term warfarin therapy for antiphospholipid syndrome. The patient experienced a sudden decrease in platelet count, from 308,000 per μL from the day of admission to 38,000 per μL the following day. Follow-up testing revealed unremarkable red blood cell (RBC) morphology, no evidence of platelet clumping, and negative heparin-induced antibody test results. Platelet antibody testing revealed anti-HPA15a antibodies.