Paroxysmal or persistent tachycardia in pediatric patients is a common disease. Certain circulating microRNAs (miRNAs) have been associated with arrhythmia. The present study investigated miRNAs in the plasma of pediatric patients with tachycardia. Forty pediatric subjects were included retrospectively: 24 with recurrent sustained tachycardia [seven cases of ventricular tachycardia (VT) and 17 cases of supraventricular tachycardia (SVT)] and 16 healthy controls. Circulating miR‑1 and miR‑133 in the plasma were detected by fluorescent quantitative polymerase chain reaction. miR‑1 levels were significantly decreased in the arrhythmia group compared with those in the controls (P=0.004) whilst miR‑133 expression levels were not significantly different between the two groups (P=0.456). Both miR‑1 and miR‑133 levels showed significant differences between the SVT and VT groups (P=0.004 and P=0.046, respectively), and a significant decrease in miR‑1 levels was observed in the SVT group as compared with the controls (P<0.001). No significant difference was observed in the expression levels of miR‑133. By contrast, miR‑133 levels were significantly increased in the VT group compared with those in the controls (P=0.024), whereas no statistically significant difference was observed in the expression levels of miR‑1. Receiver operating characteristic curves showed that 1/miR‑1 was significant for the evaluation of tachycardia. Additionally, miR‑1 produced enhanced sensitivity and specificity for the evaluation of SVT compared with miR‑133, whereas miR‑133 was a better marker to assess VT. This study demonstrated that miRNAs may be appropriate markers for pediatric tachycardia; miR‑1 levels were decreased in the arrhythmia group compared with those in the healthy controls. Furthermore, patients with SVT had lower miR‑1 expression levels while those with VT had higher miR‑133 expression levels.