The existence of cardiac damage in active rheumatic carditis patients is unknown, especially in those without pericarditis. The aim of this study was to determine cardiac myocyte damage using cardiac troponin T (cTnT) measurements in active rheumatic carditis. The levels of creatine kinase MB isoenzyme (CK-MB), cTnT, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), cardiothoracic ratio (CTR), and fractional shortening (FS) were compared using Mann–Whitney U test between 28 patients with active rheumatic carditis and 32 controls (healthy children). Association of cTnT levels with ESR, CRP, and CTR was evaluated with Spearman correlation analysis. ESR, CRP, cTnT levels, and CTR were statistically higher in the patients than in the controls. There were no differences between the groups for CK-MB levels and FS. No relationships were found between cTnT levels and ESR, CRP, and CTR in the patient group. The results of the study suggest that when cTnT levels are within non-pathological range, there is no serious cardiac damage; however, statistically significant increases in cTnT levels may indicate minor damages in patients with active carditis due to acute rheumatic fever.