Carboplatin hypersensitivity has rarely been reported in patients receiving repeated cycles of therapy, but has not been reported in transplant settings. We report a case of carboplatin hypersensitivity during conditioning for autologous PBSC transplantation. The patient suddenly developed chest tightness, hemoptysis, hypoxia and hypotension, resulting in a transient myocardial ischemia. The pathophysiologic mechanism for the event seemed to be non-immune-mediated direct histamine release given the lack of prior exposure to platinum. Contrary to advice not to continue further treatment with carboplatin by some authors, we successfully desensitized the patient and subsequently gave more carboplatin as a part of conditioning. Awareness of carboplatin as one of the causes of hypersensitivity may help avoid further problems either by substitution or desensitization, along with premedications.