Atrial fibrillation (AF) in lifetime athletes (e.g., ≥5 years of participation) is a growing concern but remains enigmatic. Intriguingly, a direct relationship between lifetime training hours and risk of developing AF exists. Professionals in exercise and sport science are at the forefront to help recognize symptoms and direct the athlete to appropriate medical clinicians for expedient care. Although AF in athletes is usually not accompanied by structural heart disease or stroke risk factors (i.e., termed lone AF), it may, nonetheless, pose health risks. In this study, we review various types of AF, proposed mechanisms, and treatment strategies for athletes with AF.