Background & Objective: Bacterial, contamination of blood components are a significant risk for transfusion reactions. Inherently, platelet concentrates (PCs) are vulnerable to bacterial contamination, due to the storage condition of processed PCs at room temperature, which provide very suitable conditions for the proliferation of microorganisms. The current study aimed at investigating the transfusion associated septic reaction rate in patients with hemato-oncological diseases in Imam Khomeini Hospital, Tehran, Iran, and identifying the contaminating bacteria. Methods: A total of 3056 adult patients of the Cancer Center of Imam Khomeini Hospital in Tehran transfused with PCs were studied based on the clinical symptoms of septic transfusion reaction from June 1, 2010 to May 31, 2011. Patient presented with the criteria of reaction and the residual components were evaluated for bacterial contamination by Bac T/Alert system. Results: Patients with leukemia or lymphoma transfused with random-donor PCs were evaluated the signs and symptoms of transfusion reaction occurred only in 12 (%0.4) cases. Automated cultivation found 3 positive blood cultures. Among these a male recipient was categorized as possible septic transfusion reaction and Citrobacterfreundii was isolated from blood sample. Conclusion: Appropriate clinical utilization of PCs transfusion, and ongoing vigilance to recognize, investigate, promptly treat, and report all suspicious transfusion reactions are necessary to manage the transfusion complication including transfusion-transmitted infections (TTI).