Introduction Benign cardiac rhabdomyomas are the most common cardiac tumors in fetuses and children. They are most often located in the ventricles and may disturb myocardial function, the severity correlating with location and size of the tumor. Rhabdomyomas are commonly associated with the tuberous sclerosis complex (TSC) and are the first clinical manifestation in 50–80% of the cases [Isaacs H Jr. Fetal and neonatal cardiac tumors. Pediatr Cardiol. 2004;25:252–73, Colosi E, Russo C, Macaluso G, Musone R, Catalano C. Sonographic diagnosis of fetal cardiac rhabdomyomas and cerebral tubers: a case report of prenatal tuberous sclerosis. J Prenat Med. 2013;7:51–5]. Several authors have documented the sensitivity of TSC-associated rhabdomyomas to everolimus treatment [Hoshal SG, Samuel BP, Schneider JR, Mammen L, Vettukattil JJ. Regression of massive cardiac rhabdomyoma on everolimus therapy. Pediatr Int. 2016;58:397–9, Mlczoch E, Hanslik A, Luckner D, Kitzmüller E, Prayer D, Michel-Behnke I. Prenatal diagnosis of giant cardiac rhabdomyoma in tuberous sclerosis complex: a new therapeutic option with everolimus. Ultrasound Obstet Gynecol. 2015;45:618–21, Tiberio D, Franz DN, Phillips JR. Regression of a cardiac rhabdomyoma in a patient receiving everolimus. Pediatrics. 2011;127:e1335–7]. The present study provides convincing evidence of successful everolimus therapy in a newborn without the TSC complex. Case presentation A cardiac rhabdomyoma measuring 35 × 28 × 24 mm was seen in a fetus in pre- and postnatal echocardiography. There was no family history for TSC and amniocentesis showed no mutations in the TSC1 / TSC2 genes. Off-label treatment with everolimus began when the neonate was 11 days old and was discontinued when the infant was 11 months old after echocardiography showed marked regression of tumor size and improvement of the tricuspid valve insufficiency. Echocardiography 3 months later showed an increase in size to 13.2 × 9 mm, so that everolimus therapy was re-instated. The next echocardiography, 10 weeks later, showed renewed regression of tumor size and a residual moderate tricuspid valve insufficiency under everolimus therapy. Discussion The present report of a rhabdomyoma in a newborn without an association with TSC is of interest because it identifies a treatment effect of everolimus. A medical approach in patients with cardiac decompensation due to intracardiac rhabdomyomas offers an attractive alternative to surgery.