Background: Contamination of donated blood is considered a serious health problem. The term (Bacterial contamination) is the existence of bacteria in the blood or its products that are collected in blood bags and stored for transfusion. Blood bags prepared for transfusion should be free from micro-organisms. Blood collection and processing must be done under complete aseptic conditions and techniques. However, sources of the donated blood contamination may be endogenous (the source of contamination is from the donors) or exogenous source (during the collection and processing Objectives: This study aimed to estimate the rate of contamination, and identify the types of micro-organisms detected in the blood products prepared for transfusion and to detect antimicrobial susceptibility (antibiotic sensitivity tests) ) of contaminant agents in blood of blood bank bags. Methodology: After adoption of Local Institutional Ethical Committee of Menoufia University Hospital, this study was established at the blood bank of Menoufia University Hospital, Egypt. Over eighteen months from April 2018 to October 2019. One hundred donor's blood samples were withdrawn for culture to detect bacterial growth. In addition, the antibiotic sensitivity tests of the growing micro-organisms were performed. Results: From the 100 sample donor blood, 12 blood bags (12%) showed isolates of different bacteria. Eight of the isolated bacteria were Gram-positive cocci representing 66.7%. Conclusion: The predominantly isolated bacteria were Coagulase-negative Staphylococcus and Staphylococcus aureus. Staph aureus was resistant to ampicillin and cotrimoxazole by susceptibility tests.