Aortic coarctation is a congenital heart disease that causes an increased left ventricular afterload, resulting in increased systolic parietal tension, compensatory hypertrophy, and left ventricular systolic and diastolic dysfunction. The speckle tracking is a new echocardiographic technique that allows the detection of subclinic left ventricular systolic dysfunction. The aim of this study was to detect early left ventricular dysfunction using mechanical deformation by echocardiography in adults with un-repaired aortic coarctation. A total of 41 subjects were studied, 20 patients with aortic coarctation and 21 control subjects, 21 women (51.2%), with an average age of 30 ± 10 years. All patients with aortic coarctation had systemic arterial hypertension (p < 0.001). Seventy percent (14/20) of the patients had bicuspid aortic valve. Statistically significance (p < 0.005) were found in left ventricular mass index, E/e ratio, pulmonary artery systolic pressure and peak velocity and maximum gradient of the aortic valve. The global longitudinal deformation of the left ventricle in patients with aortic coarctation was significative decreased, p < 0.001. The ejection fraction and the global longitudinal deformation of the left ventricle were significantly lower in patients with aortic coarctation compared to the control group, p < 0.003, p < 0.001, respectively. The subgroup of patients with coarctation and left ventricular ejection fraction < 55% had a marked decrease in global longitudinal strain (− 15.9 ± 4%). The radial deformation was increased in patients with aortic coarctation and showed a trend to be significant (r = 0.421; p < 0.06). A significant negative correlation was observed between the global longitudinal deformation and left ventricular mass index (r = 0.54; p = 0.01) in the aortic coarctation group. The patients with aortic coarctation and left ventricular hypertrophy had marked reduction of left ventricular global longitudinal deformation (− 16%, p < 0.05). In our study patients with normal left ventricular ejection fraction had abnormal global longitudinal deformation and also the increased left ventricular mass was related with a decreased left ventricular global longitudinal deformation as a sign of subclinical systolic dysfunction.