Particulate matter (PM) emitted from incense burning is a serious problem because of its effects on human health and the environment, especially on the air quality of Southeast Asia. This study investigated the PM1 and PM2.5 concentrations in two temples in Vietnam and Taiwan, focusing on events (i.e., new moon and full moon day) and non-event days using PM sensors. Moreover, PM2.5 samples were collected to determine organic carbon (OC) and elemental carbon (EC) concentrations. The PM1 and PM2.5 concentrations in Vietnam (22.7 ± 18.7 and 36.5 ± 33.9 µg m–3, respectively) were lower than those at the Taiwan temple (74.5 ± 53.4 and 97.0 ± 65.4 µg m–3, respectively). The incense burning activity in the Taiwan temple occurred inside the temple while the incense burner at Vietnam’s temple was located outdoors. During the event days, PM1 and PM2.5 concentrations were about two times greater than on non-event days, highlighting the impact of incense burning on the PM concentrations. By breaking the study area into control and exposure sites, we found that the people inside the temple experienced 2–5 times higher PM concentrations as compared to those in the ambient air. The PM1/PM2.5 ratio was 0.6 ± 0.1 for the Vietnam temple, which was lower than the Taiwan value (0.7 ± 0.1). The OC and EC concentrations in the Taiwan temple were 129.40 ± 97.68 and 1.16 ± 2.31 µg m–3, respectively, significantly greater than those found in the Vietnam temple (OC = 27.70 ± 7.66 µg m–3, EC = 1.63 ± 0.93 µg m–3). Furthermore, the OC/EC ratio in the Vietnam temple (20.24) was similar to those reported from incense and biomass in previous research. The increase in religious activities was the major factor leading to the enhancement of the air pollutant levels surrounding the study areas. This study provides valuable information on PM and carbonaceous aerosols emitted from incense burning in Southeast Asia megacities.