© 2019 International Society of Travel Medicine 2019. All rights reserved. For Permissions, please e-mail: email@example.com. Background: With the number of annual global travellers reaching 1.2 billion, many individuals encounter greater levels of air pollution when they travel abroad to megacities around the world. This study's objective was to determine if visits to cities abroad with greater levels of air pollution adversely impact cardiopulmonary health. Methods: A total of 34 non-smoking healthy adult participants who travelled abroad to selected cities from the New York City (NYC) metropolitan area were pre-trained to measure lung function, blood pressure and heart rate (HR)/HR variability (HRV) and record symptoms before, during and after travelling abroad. Outdoor particulate matter (PM)2.5 concentrations were obtained from central monitors in each city. Associations between PM exposure concentrations and cardiopulmonary health endpoints were analysed using a mixed effects statistical design. Results: East and South Asian cities had significantly higher PM2.5 concentrations compared with pre-travel NYC PM2.5 levels, with maximum concentrations reaching 503 μg/m3. PM exposure-related associations for lung function were statistically significant and strongest between evening Forced Expiratory Volume in the first second (FEV1) and same-day morning PM2.5 concentrations; a 10-μg/m3 increase in outdoor PM2.5 was associated with a mean decrease of 7 mL. Travel to a highly polluted city (PM2.5 > 100 μg/m3) was associated with a 209-ml reduction in evening FEV1 compared with a low polluted city (PM2.5 < 35 μg/m3). In general, participants who travelled to East and South Asian cities experienced increased respiratory symptoms/scores and changes in HR and HRV. Conclusions: Exposure to increased levels of PM2.5 in cities abroad caused small but statistically significant acute changes in cardiopulmonary function and respiratory symptoms in healthy young adults. These data suggest that travel-related exposure to increased PM2.5 adversely impacts cardiopulmonary health, which may be particularly important for travellers with pre-existing respiratory or cardiac disease.