Introduction The incidence of new-onset atrial high-rate episode (AHRE) is higher among patients with cardiac implantable electronic devices (CIEDs) than in the general population. We sought to elucidate the clinical factors including P-wave dispersion (PWD) in sinus rhythm associated with AHRE in CIED patients. Methods and results One hundred one patients with newly implanted CIEDs from 2010 to 2014 at our institute were included. PWD was measured at the time of device implantation via a body-surface electrocardiogram. AHRE was defined as any episode of sustained atrial tachyarrhythmia (>170 bpm) recorded in the device’s memory. Patients were divided into an AHRE group (n=34) and non-AHRE group (n=67) in accordance with the presence or absence of AHRE within one year of device implantation and compared. The mean age was 75 ± 11 years old. A greater incidence of sick sinus syndrome (p=0.05) and longer PWD (62.6 ± 13.1 vs. 38.2 ± 13.9 ms; p<0.0001) were apparent in the AHRE group. Multivariate analysis revealed that PWD was an independent predicting factor for new-onset AHRE (odds ratio: 1.11; 95% confidence interval: 1.06–1.17; p<0.0001). In the logistic regression analysis, the receiver-operating characteristic curve (area under the curve: 0.90; p<0.001) suggested the best cutoff value for PWD was 48 mm, achieving a sensitivity of 73.8% and specificity of 77.9%. Conclusion PWD is a simple but feasible predictor for new-onset AHRE in patients with cardiac implantable electronic devices.