Alpha one anti-trypsin (A1AT) is a major serine protease inhibitor found circulating in human blood. A1AT related studies mainly focus on A1AT potential biomarker as well as therapeutic target in non-infectious diseases. Their findings indicate A1AT beneficial features may also be applied for monitoring and treating infectious disease. However, only a few studies have reviewed A1AT’s useful properties as a biomarker and therapeutic agent for infectious diseases. This narrative review aims to summarize growing evidences that support the idea of utilizing A1AT as a tool for monitoring and therapy for infectious diseases. A1AT showed potential as a biomarker for a wide spectrum of infectious disease, from virus, bacteria, to parasite. Its level and functionality were proposed to predict risk for disease susceptibility or progression and to indicate response therapy. As promising therapeutic agent in various infectious diseases, the administration of A1AT has shown antimicrobial activity, immunomodulatory and anti-apoptotic effect, in addition to more familiar function, suppressing excessive proteolysis. The broad utilization of A1AT, both as biomarker and therapeutic agent, in studies on infectious diseases seems promising. However, there are issues need to be investigated further before establishing its feasibility as a monitoring and therapy tool against infection diseases . J Microbiol Infect Dis 2019; 9(1): 51-58.