Atrial premature complexes (APCs) serve as acute triggers for atrial fibrillation (AF), but it is currently unknown whether the association between APCs and AF varies by race or sex. We examined the association between APCs and AF in 13,840 (mean age = 63 ± 8.4 years; 56% women; 37% black) participants from the REasons for Geographic And Racial Differences in Stroke study. APCs were detected on baseline electrocardiograms (2003 to 2007). Incident AF was identified by study-scheduled electrocardiograms and self-reported history at a follow-up examination. Logistic regression was used to compute odds ratios (OR) and 95% confidence intervals for the association between APCs and incident AF. A total of 950 participants (6.9%) had APCs at the baseline visit. After a median follow-up of 9.4 years, 1015 incident AF cases (7.3%) were detected. APCs were associated with an increased risk of AF (odds ratios = 1.92, 95% confidence intervals = 1.57, 2.35). The relation between APCs and AF did not vary by race (interaction p value = 0.56) or sex (interaction p value = 0.66). In conclusion, APCs detected on a routine electrocardiogram are associated with an increased risk of AF development, and this association does not vary by race or sex. The findings of this analysis suggest that the risk of AF associated with atrial ectopy does not account for the differential risk of AF that is observed in whites compared with blacks, and in men compared with women.