Rheumatic heart disease (RHD) is a major cause of morbidity and mortality in developing countries, so early diagnosis and treatment can reduce morbidity and mortality resulting from subsequent valvular damage. The aim of this study was to detect subtle myocardial dysfunction among children with RHD with preserved left ventricular systolic function. This is a cross-sectional case–control study that was conducted on 30 children with RHD (who had valvular affection of any degree and were not in activity) compared to 23 healthy children. After history taking and cardiac examination, 2D echocardiography, tissue Doppler imaging, 3D-echocardiography and 3D speckle tracking echocardiography were done to both groups, whereas cardiac magnetic resonance imaging was done only to the patient group. The 3D-derived left ventricular end-diastolic volume and sphericity index among patients were significantly increased when compared to controls [131.5 (101.5 to 173.7) vs. 69 (58 to 92), P = 0.001, and 0.46 (0.36 to 0.59) vs. 0.33 (0.29 to 0.38), P = 0.001, respectively]. The 3D-derived ejection fraction and longitudinal strain did not differ significantly among both groups. The 3D-derived global circumferential strain was higher in patients when compared to controls [− 14 (− 16 to − 10) vs. − 11(− 13 to − 10), P = 0.04]. None of the examined patients demonstrated late enhancement myocardial fibrosis. In children with RHD and preserved systolic function, subtle systolic dysfunction could not be detected using conventional and novel non-conventional methods. This may indicate that the myocardial affection during the acute stage of rheumatic carditis is minimal with almost complete resolution.