The acute effects and the time course of fine particulate pollution (PM₂.₅) on atrial fibrillation/flutter (AF) predictors, including P-wave duration, PR interval duration, and P-wave complexity, were investigated in a community-dwelling sample of 106 nonsmokers. Individual-level 24-h beat-to-beat electrocardiogram (ECG) data were visually examined. After identifying and removing artifacts and arrhythmic beats, the 30-min averages of the AF predictors were calculated. A personal PM₂.₅ monitor was used to measure individual-level, real-time PM₂.₅ exposures during the same 24-h period, and corresponding 30-min average PM₂.₅ concentration were calculated. Under a linear mixed-effects modeling framework, distributed lag models were used to estimate regression coefficients (βs) associating PM₂.₅ with AF predictors. Most of the adverse effects on AF predictors occurred within 1.5-2 h after PM₂.₅ exposure. The multivariable adjusted βs per 10-μg/m³ rise in PM₂.₅ at lag 1 and lag 2 were significantly associated with P-wave complexity. PM₂.₅ exposure was also significantly associated with prolonged PR duration at lag 3 and lag 4. Higher PM₂.₅ was found to be associated with increases in P-wave complexity and PR duration. Maximal effects were observed within 2 h. These findings suggest that PM₂.₅ adversely affects AF predictors; thus, PM₂.₅ may be indicative of greater susceptibility to AF.