Objective The objective of this study was to derive normal electrocardiographic values and to report the abnormal findings in a large contemporary European cohort of physically active children and young adolescents. Methods In a 3-month period, data derived from subjects aged between 3 and 14 years and referred to the Telecardiology Centre (Genoa, Italy) for electrocardiogram (ECG) evaluation as pre-participation screening for non-competitive sports were analyzed. Results A total of 2060 ECGs were recorded. Of those, 1962 did not show any morphological abnormality and were used to derive normality ranges for heart rate, PR interval, QRS duration, corrected QT interval, and voltage of R wave as measured in V1 according to age and sex. Findings and clinical implications of the 98 ECGs with abnormal findings were also reported. Abnormal ECG findings were not as uncommon as expected in this population, being manifest in about 5 % of subjects. However, major ECG anomalies (diffuse negative T-waves, pre-excitation) were present in just ten subjects (0.5 %). Lower mean heart rate values (from 90–100 bpm at 3 years of age to 80–85 bpm at 14 years of age) and lower rates of the prevalence of negative T-waves in the V3 lead (from 55–60 % at 3 years of age to 8–10 % at 14 years of age) were observed with increasing age. Conclusions This is the first work reporting derived normal limits and abnormal ECG findings in a large contemporary European cohort of children and adolescents aged 3–14 years practicing non-competitive sports. Clear pathological alterations are extremely uncommon, deserving, when encountered, additional examinations. Even in a physically active population, the common features of an adult athlete’s ECG are absent.