Introduction: bloodstream infections are one of the leading causes of mortality in children and adults worldwide. Blood cultures are essential diagnostic tests for identifying microorganisms and guiding antimicrobial treatment. However, sample contamination reduces diagnostic accuracy due to the introduction of contaminating organisms during sample collection or the patient's clinical condition.Methods: a systematic review was conducted following the PRISMA guidelines on studies found in PubMed, Scielo, Scopus, Web of Science, and BVS, including a total of 19 studies.Results: after reviewing the 19 studies, detailed information was gathered on a standardized protocol for the proper collection of blood samples for blood cultures in adult and pediatric patients. Additionally, internal and external risk factors associated with specimen contamination were analyzed. Some of these factors included the severity of the patient's condition, the immune system, the use of invasive devices, skin antisepsis, technical difficulties, or high workload.Conclusions: this research highlights the importance of rigorous implementation of standardized procedures to minimize risk factors associated with blood culture contamination and, consequently, the prevention of unnecessary treatments.