Objective: Our aim was to evaluate left ventricular (LV) mechanics by using speckle tracking echocardiography (STE) in asymptomatic patients with abnormal origin of the left main coronary artery from the pulmonary trunk (ALCAPA), late after successful repair, in the presence of LV ejection fraction (EF) >50%. Methods: We studied 30 ALCAPA patients (median age 4 years, range 1-25 years, NYHA class I, LVEF >50%) and 16 healthy age- and sex-matched controls (median age 5 years, range 1-25 years). All underwent standard echocardiographic evaluation and STE. Results: LV dimensions and LVEF (63.6 ± 8.2% vs. 64.1 ± 5.1%, p = 0.826) were not different between patients and controls. Diastolic parameters were significantly abnormal in our patients versus controls (E/e' average: 11.9 ± 5.8 vs. 6.6 ± 3.0, p = 0.0014). Global LV longitudinal strain was significantly lower in ALCAPA patients versus controls (-17.6 ± 3.5% vs. -23.4 ± 3.1%, p < 0.0001). LV torsion (9.1 ± 4.9° vs. 11.9 ± 3.3°, p = 0.046) was significantly impaired in ALCAPA patients. Conclusions: After successful repair in asymptomatic ALCAPA patients, despite an LVEF >50%, diastolic function, LV longitudinal deformation and LV torsion remain impaired. We suggest including a detailed study of the diastolic function and cardiac mechanics in the clinical follow-up of these patients to identify the subgroup of patients at higher risk.