Rhabdomyomas are the most common primary cardiac tumors in infants and children. They are usually associated with tuberous sclerosis (TS). As the tumors tend to regress spontaneously, surgical intervention is not usually performed unless they become obstructive or cause incessant arrhythmias. We report an extremely rare case of rhabdomyoma serving as a substrate for Wolff-Parkinson-White (WPW) syndrome and intractable supraventricular tachycardia accompanied by TS. Our case is particularly interesting because it was diagnosed prenatally. The signs of WPW syndrome disappeared from the electrocardiogram with the regression of the tumor.