© 2021 Wolters Kluwer Medknow Publications. All rights reserved.Background: Congenital myopathies (CMs) are a group of rare genetic muscle disorders. Cardiac involvement can be seen in these patients. We aimed to evaluate the myocardial strain parameters by 2D speckle-tracking echocardiography (STE) in patients with CM. Materials and Methods: Twenty-four patients with CM whose diagnosis was confirmed by genetic analysis or muscle biopsy were included in the study, and 48 patients were involved as a control group. Left ventricular ejection fraction (LVEF%) was calculated by biplane Simpson method, and myocardial strain analysis was performed by 2D STE. Results: The median age of the study population was 26 (19-35 interquartile range [IQR]) and 43 (60%) were women. In the analysis performed after the exclusion of two patients with multiminicore disease (MMD) who developed heart failure, although mild, LVEF% (62 [60-65 IQR] vs. 64 [63-66 IQR], P = 0.008) and right ventricular global longitudinal strain (RVGLS) were significantly lower in the CM group (-21.8 [-19.7, -24.9 IQR] vs. -23.9 [-22.4, -25.6 IQR], P = 0.0017). Left ventricular global longitudinal strain (LVGLS) was observed similarly in both groups (-19.9 [-18.7, -20.7 IQR] vs. -20.5 [-19.3, -21.9 IQR], P = 0.069). LVEF% (33 and 46), LVGLS (-7.5 and -10.7), and RVGLS (-14.9 and -16.1) values were low in two siblings with MMD. Conclusion: Although LVEF% and RVGLS were significantly lower in the CM group, LVGLS was similar. The decrease in RVGLS and LVEF% was mild, and heart failure was not observed in any patient except MMD patients who were not included in the analysis.