Various rhythm and conduction abnormalities can develop in acute rheumatic fever. This study investigated rhythm and conduction abnormalities in children with acute rheumatic fever using a standard 12-lead electrocardiogram and 24-h rhythm Holter recordings. This multicenter retrospective study, performed between August 2011 and March 2012, enrolled 73 consecutive children with acute rheumatic fever. Standard electrocardiography was used to measure PR and corrected QT intervals. Holter recordings were evaluated for all the patients, and 52 of the patients (71.2 %) had carditis that was either isolated or together with other major criteria. A positive correlation was detected between carditis and the mean PR interval on standard electrocardiography, but this was not significant (p > 0.05). Standard electrocardiography showed a significant positive correlation between PR and corrected QT intervals (p = 0.03; r = 0.55). Standard electrocardiography showed only three patients (4.2 %) with premature contractions, whereas 24-h electrocardiography showed 26 patients (35.6 %) with premature contractions. Carditis was positively correlated with premature contractions (p < 0.01; r = 0.57). One patient with junctional rhythm and one patient with left bundle block were detected by standard electrocardiography. Whereas some patients with carditis exhibited no arrhythmic evidence on standard electrocardiograms, complete atrioventricular block, supraventricular tachycardia, and Mobitz type 1 block were observed on 24-h Holter recordings. A positive correlation also was observed between the presence of premature contractions and serum levels of acute-phase reactants (p = 0.03; r = 0.62). These findings led to the conclusion that rhythm and conduction disorders in acute rheumatic fever are more common than previously thought.