Outdoor air pollution is a leading cause of death and premature death globally. Motorcycle-taxi drivers were most at risk associated with occupational exposure to ambient air pollution in urban areas. Therefore, a cross-sectional study was conducted to determine the influencing factors and prediction of lung function impairment in 308 motorcycle-taxi drivers living in Bangkok and adjacent provinces between February and June 2022. The study design included: data collection using questionnaires applied from the Thai version of ATS-DLD-78A: American Thoracic Society Division of Lung Diseases and Department of Disease Control, Ministry of Public Health, Thailand; a collection of respirable dust, and ambient air pollution parameters measured by per-sonal air sampling pump and real-time air quality index (AQI) station, and lung function determined by the spirometer. The results showed that 14 factors were significantly associated with lung function impairment (p<0.05). Apparently, seven influencing factors showing the most association were included: gender, the height of the subjects, history of allergies, exposure to respirable dust, mask types, helmet types, and family history of lung disease. The lung function impairment of motorcycle-taxi drivers was significantly predicted in 28.1% by regression analysis of these seven variables (R2=0.281). Therefore, this is the first report on influencing factors and prediction of lung function impairment among motorcycle-taxi drivers. These findings would be very useful for preventing and controlling measure ambient air pollution, setting policies and strategies to mitigate the risks for motorcycle-taxi drivers and the other ex-posed population.