Objectives: To determine the prevalence of rheumatic heart disease (RHD) in school‐aged children and young people in Timor‐Leste.

Design: Prospective cross‐sectional survey. Echocardiography was performed by Australian cardiologists to determine the presence of RHD. Demographic data were also collected. Patients in whom RHD was detected were entered into a register to allow monitoring of adherence to secondary prophylaxis; the first dose of benzathine penicillin G (BPG) was administered on the day of screening.

Setting: Schools in urban (Dili) and rural (Ermera) Timor‐Leste.

Participants: School students aged 5–20 years.

Outcome measures: Definite and borderline RHD, as defined by World Heart Federation echocardiographic criteria.

Results: 1365 participants were screened; their median age was 11 years (IQR, 9–14 years), and 53% were girls. The estimated prevalence of definite RHD was 18.3 cases per 1000 population (95% CI, 12.3–27.0 per 1000), and of definite or borderline RHD 35.2 per 1000 (95% CI, 26.5–46.4 per 1000). Definite (adjusted odds ratio [aOR], 3.5; 95% CI, 1.3–9.4) and definite or borderline RHD (aOR, 2.7; 95% CI, 1.4–5.2) were more prevalent among girls than boys. Eleven children (0.8%) had congenital heart disease. Of the 25 children in whom definite RHD was identified, 21 (84%) received education and a first dose of BPG on the day of screening; all 25 have since received education about primary care for RHD and have commenced penicillin prophylaxis.

Conclusions: The rates of RHD in Timor‐Leste are among the highest in the world, and prevalence is higher among girls than boys. Community engagement is essential for ensuring follow‐up and the effective delivery of secondary prophylaxis.