Patients with repaired Tetralogy of Fallot (rToF) can have significant right and left ventricular dysfunction which can impact clinical outcome. Conventional echocardiographic evaluation using ejection fraction can be limited in detecting early stages of deteriorating left ventricular (LV) systolic function. Speckle-tracking echocardiography (STE) provides a promising emerging tool for early detection of LV systolic dysfunction. The aim of this cross-sectional study is to evaluate the left ventricular global and regional function using STE in rToF patients with preserved left ventricular ejection fraction to detect early signs of LV dysfunction. The study is a retrospective review of the medical records and transthoracic echocardiograms of rTOF patients who were seen in the pediatric cardiology clinic at our institution from August 2016 till May 2018. The rTOF group was compared with a matched healthy control group. Offline strain analysis of TTE studies was completed in each subject according to mode set by the American Society of Echocardiography. Twenty-two patients with rTOF and 22 age-matched controls (rTOF 18.7 ± 6 years and control 14.6 ± 9.6 years, P value 0.19) were included during the study period. The rTOF group consisted of 12 males and 10 females, whereas the control group consisted of 15 males and 7 females. There was no significant difference in terms of LV ejection fraction using both 2-chamber as well as 4-chamber views. Global LV longitudinal strain was significantly lower in the rTOF group compared with the control group (rTOF − 15.92 ± 3.16 vs control − 22.79 ± 2.45, P value 0.00). All 17 segments showed significantly lower longitudinal strains in rTOF group compared with the control group. Global circumferential left ventricle strain was significantly lower in the rTOF patients compared with the control group (− 17.24 ± 5.86 vs − 22.74 ± 3.99, P value 0.001). 13 out of 16 segments had lower circumferential strains in the rTOF patients compared with controls. Asymptomatic surgically repaired TOF patients exhibited abnormal segmental and global left ventricle longitudinal and circumferential strains despite having normal left ventricle ejection fraction. Our findings suggest subclinical damage to the left ventricle systolic function post-surgical repair of TOF. 2-D speckle-tracking echocardiography may be used as a valuable method in the early recognition of left myocardial systolic function impairment in patients after TOF repair. The application of this method to guide clinical decision and management of rTOF patients such as earlier pulmonary valve replacement or risk stratification for sudden cardiac death needs further investigation.