Introduction: This study aimed to evaluate the cardiac function of fetuses with congenital diaphragmatic hernia by conventional echocardiography and spectral tissue Doppler imaging (s-TDI) and to evaluate the relationship between cardiac function and the severity of pulmonary hypoplasia. We also aimed to investigate the effect of diaphragmatic hernia side on fetal cardiac function. Methods: Fetal cardiac function were evaluated in 28 fetuses (20 with left-sided and 8 with right-sided) complicated with isolated congenital diaphragmatic hernia (CDH) and 56 gestational age matched control in this single center prospective study. s-TDI measurements were obtained at the right atrioventricular valve annulus. The annular peak velocities and their ratios, the time periods of cardiac cycle and myocardial performance index were calculated. Results: In comparison to controls, significantly prolonged isovolumetric contraction time (ICT ') and isovolumetric relaxation time (IRT ') and, significantly shortened ejection time (ET ') were observed in fetuses with CDH by s-TDI. Fetuses with CDH also had higher myocardial performance index (MPI ') z-scores compared to controls. There were no significant differences in terms of s-TDI cardiac function parameters between fetuses with right- and left-sided CDH. In correlation analysis, a significant positive correlation was found between ET ' value and o/e LHR. Conclusion: The signs of both systolic and diastolic altered function were observed in fetuses with CDH with s-TDI independent of the side of the hernia, and a significant positive correlation was observed between fetal cardiac systolic function and the severity of pulmonary hypoplasia.