This study aimed to quantify paradoxical interventricular septal motion (PSM) among 20 patients following tetralogy of Fallot (TOF) repair without severe pulmonary regurgitation and 20 age-matched normal subjects. PSM was quantified using the echocardiography-derived paradox index. Tissue Doppler-derived strain rate was used to assess the longitudinal and radial systolic function of the interventricular septum (IVS). The tissue Doppler-derived Tei index was used to assess the global left ventricular function. Compared to the control group, the paradox index in patients after repair of TOF was significantly higher (p = 0.001), whereas the regional IVS longitudinal (p = 0.02) and radial (p = 0.001) systolic strain rate peaks were significantly reduced. The paradox index in the patient group correlated inversely with the IVS radial peak systolic strain rate (r = −0.64, p = 0.004) and positively with QRS duration (r = 0.50, p = 0.02). The left ventricular (LV) Tei-index correlated significantly with the paradox index (r = 0.71, p = 0.001) and with the septal radial systolic strain rate peak (r = 0.59, p = 0.004). We conclude that electrical delay and reduced regional septal systolic function were the main causes for paradoxical septal motion among patients following TOF repair without significant pulmonary regurgitation. The reduced LV systolic function among this group of patients is mainly secondary to diminished septal systolic function and the paradoxical septal motion.