Cardiac rhabdomyoma can be subclinical or fatal depending on the onset age, involving site, and the size and degree of invasion. Although most rhabdomyomas become smaller with time, emergency intervention is indicated when severe obstruction induces hemodynamic instability. Mammalian target of rapamycin (mTOR) inhibitors have been used to treat neonates and children with hemodynamically obstructive cardiac rhabdomyoma. Herein, we report a premature neonate at the gestational age of 30 + 4 weeks with severe left ventricular outflow tract obstructive cardiac rhabdomyoma who was successfully treated with the mTOR inhibitor sirolimus. To the best of our knowledge, this is the first recorded case of a premature neonate with obstructive cardiac rhabdomyoma who was successfully treated with an mTOR inhibitor. Therefore, sirolimus could be considered as an alternative medical option for managing premature neonates with obstructive cardiac rhabdomyoma.