The study aimed to investigate PM2.5-bound heavy metals and their possible health risk to the residents in the roadside areas of Bangkok, Thailand, The PM2.5 samples were collected in Prawet and Pathumwan districts between February 1 to March 8, and May 15 to October 20, 2023. The concentrations of heavy metals in PM2.5 were observed in descending order as follows: Al > Zn > Ba > Fe > Pb > Mn > As > Cr > Cu > Cd > Ni > V > Co. Among these, Al exhibited the highest concentration (1,050.40 ± 358.73 ng/m3), while Co showed the lowest (0.10 ± 0.04 ng/m3). Non-carcinogenic risk of the residents living in roadside areas particularly exposed PM2.5-bound heavy metals surpassed acceptable criteria in Prawet and Pathumwan districts, with the HI values of 1.84 (95% CI = 1.48 – 2.21), and 1.88 (95% CI = 1.46 – 2.30), HI values of both districts exceed the safe threshold for children and adults. The lifetime cancer risk (LCR) of exposure to As, Cd, Cr, Co, Pb, and Ni for adults has surpassed acceptable criteria in both districts, with the LCR values of 2.56 × 10–5 (95% CI = 1.93 × 10–5–3.18 × 10–5) and 2.88 × 10–5 (95% CI = 2.12 × 10–5–3.18 × 10–5), respectively. Heavy metals pose carcinogenic risks to adults through the inhalation pathway, representing a significant threat to the residents of Bangkok City. From principal component analysis (PCA), the potential sources of PM2.5-bound heavy metals were vehicle emissions, soil dust, crustal resuspension, industrial emissions, and crustal elements.