To report findings from the High Performance Sport New Zealand cardiac screening programme, including comparisons between sexes and ethnicities.Retrospective cohort study.Elite Olympic-sport athletes were screened (2012-2022) with personal/family history, physical examination, resting 12-lead ECG and followed from the date of first screening until July 2022. An audit reviewed screening records, including demographic data, ECGs, follow-up and diagnoses. Flagged/equivocal ECGs were re-reviewed (International Criteria).2075 ECGs from 1189 athletes (53 % female, mean age 21 years; 83 % European, 9 % Māori, 5 % Pacific Islander, 3 % other) were included. No athletes retired for cardiac reasons; there were no cardiac deaths or major cardiac incidents (mean follow-up from first screening: 6.1 years (range: 0.6-10.9 years)). Diagnoses included Wolff-Parkinson-White (WPW) syndrome (0.7 %) and cardiomyopathies (0.3 %). Overall, 3.5 % of ECGs were abnormal, with ECGs of females more commonly abnormal (4.4 % vs 2.5 %, p = 0.02) and with a higher proportion of ECGs with abnormal T-wave inversion (TWI) (3.1 % vs 0.9 %, p < 0.001) compared to males. Of the abnormal TWI in females (all aged ≥16 years), 47 % was limited to V1-V3 with no other abnormalities. Abnormality rates were similar between Māori, Pacific Islander and European athlete ECGs.WPW was the most frequent diagnosis, with very little cardiomyopathy found. The proportion of abnormal ECGs was low overall, but higher in females. This was driven by anterior TWI in V1-V3 which was not associated with diagnoses of conditions associated with sudden cardiac death (SCD). There was no difference in the proportion of abnormal ECGs of Māori or Pacific Island athletes compared to European athletes.