Air pollution is an environmental threat to public health. This study aimed to assess PM2.5 concentrations in various microenvironments and identify their influence on personal PM2.5 exposure among schoolchildren in Vietnam. We used portable PM2.5 monitors (AirBeam3) for personal PM2.5 measurements of children aged 11–12 years living in two districts (defined as Group A and B) in Ho Chi Minh City, Vietnam, between December 2022 and January 2023, with children's activities recorded in diaries. Linear mixed-effects models were used to identify the influence of microenvironments on children's PM2.5 exposure. Overall, eligible data from 64 children were included in the analysis. The median PM2.5 concentration measured is 25 μg/m³ and average PM2.5 concentrations peaked during 06:00–07:00 and 18:00–20:30, when traffic density is heavy. Children spent the majority of their day indoors (88.4 %). Among microenvironments, children exposed to the highest PM2.5 concentration from home incense burning, followed by eating street food on sidewalks, commuting by motorbike, and being in school classrooms, with median concentrations ranging from 36.7 to 71.1 μg/m³. Major contributors to higher PM2.5 exposure in children included incense burning at home (increase by 28.9 %), eating street food (21.2 %), and road commuting (21.1 %). Notably, motorbike commuting resulted in higher PM2.5 levels than walking or cycling. Findings highlight the importance of controlling indoor air quality. Suggestions to reduce children's PM2.5 exposure include reducing incense burning, promoting cleaner transport options, and implementing long-term urban policies, such as improving public transportation and pedestrian infrastructure.