The evidence on the association between resting heart rate (HR) and incident atrial fibrillation (AF) is conflicting. Whether change in resting HR is associated with incident AF is unknown. We evaluated 11,545 participants (mean [±standard deviation] age: 57 ± 5.7 years) free of AF at baseline (1990 to 1992). Resting HR was obtained from 10-second electrocardiograms at baseline and 3 years later. AF diagnosis was ascertained from visit electrocardiograms, hospital discharge records, and death certificates through 2013. High and low resting HR were defined as ≥80 and <55 beats/min, respectively. Increase and decrease in HR were defined as a 3-year HR difference >15 and <−15 beats/min, respectively. Over a median follow-up of 22.5 years, 1,746 (15%) participants developed AF. Both baseline high resting HR and increase in HR were independently associated with incident AF (hazard ratio = 1.2, 95% confidence interval = 1.0 to 1.5 and hazard ratio = 1.4, 95% confidence interval = 1.1 to 1.9). Increase in HR was no longer associated with incident AF after additional adjustment for incident heart failure. In stratified analyses, increase in HR was associated only with AF in participants <60 years, with bachelor's degree or above, without diabetes, and without hypertension (p values for interaction ≤0.05). In conclusion, in a middle-aged population, high resting HR is associated with higher AF risk. Increase in resting HR is also associated with higher AF risk, especially in individuals without traditional AF risk factors. Whether interventions to decrease HR can prevent AF remain to be examined.