Regular intensive training induces structural, functional, and electrical cardiac adaptations collectively known as the athlete's heart. Many electrocardiogram (ECG) findings in athletes, including sinus bradycardia, early repolarization, and increased QRS voltages, reflect benign physiological adaptation. However, some patterns overlap with features of cardiomyopathy and may pose diagnostic challenges. This state-of-the-art review examines sport-specific ECG patterns and how different training modalities influence cardiac electrical remodeling and its clinical interpretation. Endurance athletes typically exhibit changes related to chronic volume loading, such as sinus bradycardia, early repolarization, and high QRS voltages. Strength athletes more often demonstrate ECG features consistent with pressure overload, including increased QRS voltages and relatively higher resting heart rates. Mixed-sport athletes show intermediate characteristics reflecting combined dynamic and static demands. Although most findings are benign, abnormalities such as lateral, inferolateral, or anterolateral T-wave inversion warrant further evaluation. Integrating sport-specific patterns with contemporary athlete-specific ECG criteria improves diagnostic accuracy and helps identify athletes requiring additional investigation.