Teratoma arising from the pericardium is an extremely rare tumor. Intrapericardialor mediastinal teratoma if detected intrauterine in fetal life, the mortality will be less. Tumor size can be large and associated with pericardial effusion, the combination of which leads to progressive cardiac tamponade, fetal hydrops, and death. In the neonatal age group most of these tumors are benign and mediastinal teratomas despite they are benign tumor but must be treated sometimes urgently because they might grow fast. Histologically teratomas may be classified as mature or immature on the basis of the presence of immature neuroectodermal elements within the tumor. Survival was linked to the degree of immaturity in the teratoma and the risk of recurrence also appears to be related to the degree of immaturity. We present here our case who is a newly born baby girl diagnosed as having a big mass inside the pericardial sac necessitated urgent surgical excision.