Fetal arrhythmias are rare but they are an important avoidable cause of perinatal mortality. Timely diagnosis is therefore crucial, as treatment can be life saving. Careful evaluation of cardiac structure and function using different echocardiographic modalities can exclude structural cardiac anomalies as well as provide accurate information about the atrial and ventricular contraction rates, their relationship, conduction pattern and hemodynamic consequences of arrhythmia. Although observation and reassurance will suffice in a substantial proportion of pregnancies complicated by fetal arrhythmia, some will require intrauterine therapy or early delivery followed by postnatal treatment to prevent heart failure and fetal/neonatal demise. Fortunately, most common fetal arrhythmias are few of those conditions that can be managed successfully in utero with good results. In this chapter, we describe the normal and abnormal fetal cardiac rhythms, their diagnosis and prenatal management.