Sudden cardiac arrest is a rare but devastating cause of death in young adults. Electrocardiograms may detect many causes of sudden cardiac arrest, but are not routinely included in pre-athletic screening in the United States of America partly because of high rates of false-positive interpretation. To improve electrocardiogram specificity for identifying cardiac conditions associated with sudden cardiac arrest, an expert panel developed refined criteria known as the Seattle Criteria. Ours is the first study to compare standard electrocardiogram criteria with Seattle Criteria in 11- to 13-year-olds. In total, 1424 students completed the pre-athletic screening and electrocardiogram; those with a positive screen or abnormal electrocardiogram interpreted by a paediatric electrophysiologist completed further work-up. Electrocardiograms referred for additional evaluation were re-interpreted by a paediatric electrophysiologist using Seattle Criteria. Electrocardiogram abnormalities were identified in 98 (6.9%); Seattle Criteria identified 28 (2.0%). Formal evaluation confirmed four students at risk for sudden cardiac arrest (0.3%): long QT syndrome (n=2), Wolff–Parkinson–White (n=1), and pulmonary hypertension (n=1). All students with at-risk phenotypes for sudden cardiac arrest were identified by both standard electrophysiologist and Seattle Criteria. The false-positive interpretation rate decreased from 6.6 to 1.7% with Seattle Criteria. Downstream costs associated with screening using standard paediatric electrocardiogram interpretations and Seattle Criteria were projected at $24 versus $7, respectively. In conclusion, using Seattle Criteria for electrocardiogram interpretation decreases the rate of false-positive results compared with standard interpretation without omitting true-positive electrocardiogram findings. This may decrease unnecessary referrals and costs associated with formal cardiology evaluation.