<p>Air pollutants have been known as the most persistent environmental risk factors of elevated blood pressure (BP). However, most of the existing studies measured resting BP only, which is not accurate as ambulatory BP. This study investigated the effects of short-term exposure to air pollutants on ambulatory BP. Wearable devices were used to measure personal ambulatory systolic BP (ASBP) and diastolic BP (ADBP) and movement trajectories of 172 participants for one week, with a 1-min interval. Daily concentrations of the six major air pollutants were estimated at a spatial resolution of 1 km. Linear mixed-effect models and distributed lag non-linear models estimated the associations between air pollutant exposure and ambulatory BP. ASBP was positively associated with PM_2.5 (<i>β</i> = 0.010 [95% CI: 0.005, 0.015]), PM₁₀ (<i>β</i> = 0.006 [0.005, 0.008]), and SO₂ (<i>β</i> = 0.046 [0.021, 0.071]), and negatively with NO₂ (<i>β</i> = -0.009 [-0.017, -0.001]); ADBP was positively associated with PM_2.5 (<i>β</i> = 0.008 [0.005, 0.010]) and PM₁₀ (<i>β</i> = 0.003 [0.002, 0.004]), and negatively with NO₂ (<i>β</i> = -0.008 [-0.012, -0.004]), O₃ (<i>β</i> = -0.002 [-0.004, -0.001]), and CO (<i>β</i> = -0.366 [-0.652, -0.081]). At 14-h lag, ASBP and ADBP were positively associated with PM₁₀ and O₃, and negatively with NO₂. The cumulated exposure to PM₁₀ and CO was associated with ambulatory BP at all levels of concentration, while SO₂ was associated with ambulatory BP only when the concentration was over 15 μg/m³. The findings have important implications for BP management and hypertension prevention, by providing solid evidence for developing cost-effective strategies of minimizing adverse environmental exposure and improving health equity.</p>