In patients operated with atrial switch for transposition of the great arteries (TGA), the left ventricle (LV) supports the pulmonary circulation and is thus pressure unloaded. Evaluation of LV function in this setting is of importance, as LV functional abnormalities have been documented and might contribute to development of symptoms. The ventricular contraction pattern in 14 Senning-operated TGA patients and 14 healthy controls was studied using tissue Doppler and magnetic resonance imaging. In the subpulmonary LV free wall, longitudinal strain was greater than circumferential strain (−23.6 ± 3.6% vs. −19.1 ± 3.2%, p = 0.002) as in the normal right ventricle (RV) (−30.7 ± 3.3% vs. −15.8 ± 1.3%, p < 0.001), but opposite to findings in the normal LV (−16.5 ± 1.7% vs. −25.7 ± 3.1%, p < 0.001). Subpulmonary strain and strain rate values were intermediate between those in the normal LV and RV. Ventricular free-wall torsion was reduced in the subpulmonary LV compared with both the normal LV (5.7 ± 3.2° vs. 16.7 ± 5.6°, p < 0.001) and RV (5.7 ± 3.2° vs. 11.4 ± 2.6°, p < 0.05). Furthermore, early diastolic filling of the subpulmonary LV differed from that of the normal LV. The subpulmonary LV displayed predominantly longitudinal shortening, as did its functional counterpart, the normal RV. However, the degree and rate of both longitudinal and circumferential shortening were intermediate between those of the normal LV and RV. This could represent a partial adaptation to the reduced pressure load. Decreased ventricular torsion and diastolic abnormalities might indicate subclinical ventricular dysfunction.