Abstract Human exposure to airborne micro-organisms has been shown to cause various health effects, including infectious diseases, acute toxic reactions and allergies. In the past decade, several outbreaks of airborne pathogens, such as Severe Acute Respiratory Syndrome (SARS) and avian flu have raised the public's concerns about the airborne micro-organisms and called for the urgent development of fast detection and effective control techniques. Filtration is one of the most widely used methods for collecting airborne particles; however, this technique alone cannot effective inactivate the collected bio-aerosols. ZnO composite has been receiving attention recently due to its properties, which are applicable in many applications, including inactivation of micro-organisms. This study synthesized ZnO/PET composite nanofiber via electrospinning technique combined with hydrothermal process and evaluated the synthesized material for their filtration efficiency and antimicrobial property. This work is divided into 2 parts: (1) investigate the influence of synthesized conditions on the physical, chemical and anti-microbial properties of ZnO/PET nanofibers and (2) evaluate the filtration and inactivation efficiencies of the synthesized materials when exposing to airborne micro-organisms. The results showed that the hydrothermal conditions play an important role on structure of the nano-fibers, average diameter of synthesized fiber and average of zinc oxide particles, chemical properties of the composites, and subsequently their anti-microbial property. The synthesized nanofibers undergone hydrothermal temperature of 200oC for 0.5hr exhibited the highest inactivation efficiency for 3 types of bio-aerosols, including B. subtilis, P. fluorescens and S. epidermidis. The fibers that exhibited the highest inactivation efficiency via AATCC standard method were evaluated for the filtration and inactivation efficiencies of airborne bio-aerosols. The results showed that the filtration and inactivation efficiencies of the nanofiber was 99.5% and 97%, respectively.