Background Published guidelines suggest that ECG screening in US athletes may cause excessive anxiety, especially in those with false-positive findings. However, this has never been formally evaluated. Methods and study design Prospective, nonrandomised controlled trial. High school athletes received a standardised history and physical examination (control) or a history and physical examination with an ECG (experimental). Prescreen and postscreen assessments for health attitudes, anxiety and impact of screening on sport were conducted. Results 952 athletes (49.7% girls, mean age 15.5 years) participated (control=150; experimental=802). 4.4% worried about having an underlying cardiac condition, and 73% wanted to learn if they had a cardiac abnormality prior to competition. In the experimental group, 576 had normal screens, 220 had an abnormal screen (by history 15.8%, physical examination 6.2% or ECG 1.7%) but normal work up (false-positive) and 6 were identified with a serious cardiac condition (true-positive, 0.75%). Compared with the control group, those who received an ECG were more likely to: (1) be significantly more satisfied with their screening (p<0.001), (2) feel safer during competition ( p<0.01), (3) support that all athletes should receive cardiac screening ( p<0.001) and (4) state the ECG positively impacted their training (p<0.001). False-positive athletes did not report anxiety during or after screening. Distress levels did not differ based on reason for needing further evaluation (history, physical examination or ECG, p=0.311). Compared with control participants, individuals with false-positive results: (1) reported no difference in postscreen anxiety ( p=0.775), (2) felt safer during competition (p<0.001), (3) would recommend ECG screening to others (p<0.001) and (4) expressed a positive impact on training ( p<0.001). Conclusions Excessive anxiety should not be used as a reason to forego ECG screening in athletes.