To generate granular normative electrocardiogram (ECG) data and characterize the variation by ethnicity and sport played. Cross-sectional study; ECGs were collected from preseason screening programs from 2012 to 2019 and interpreted in accordance with athlete-specific guidelines. Of the professional athletes based in Vancouver, the North Shore Heart Centre performs the annual preparticipation ECG screening. Seven hundred fifty-three professional male athletes competing in hockey, football, lacrosse, skiing, and snowboarding. Independent variables include commonly transcribed electrocardiographic findings, for example, those indicating benign and pathologic findings. Prevalence of and variance in electrocardiographic findings by sport played and ethnicity. Of the 753 athletes, 171 (22.3%) were National Hockey League, 358 (47.5%) were Canadian Football League, 163 (21.6%) were Major League Soccer and/or the Canadian National Soccer team, and 61 (8%) others. The most common finding, sinus bradycardia, was more likely in both soccer (P < 0.001) and hockey (P < 0.001) versus football players. Early repolarization (ER) was more likely in soccer players versus both hockey (P < 0.001) and football players (P = 0.001). Within football, Black athletes (BA) were more likely than White athletes to display ER (P = 0.009), left ventricular hypertrophy (P = 0.004), and nonspecific ST changes (P = 0.027). Our study contributes to the generation of normative data for ECG findings while accounting for ethnic and sport-specific variation. The expected clinical presentation of endurance athletes, including soccer players, and the possible predisposition of BA to develop distinct adaptations can augment clinical care by delineating physiology from pathologic changes.