Introduction: Perinatal testicular torsion is not a frequent, but a grave finding finding. As only immediate surgical retorsion may save the viability of the testicle, time is of essence. We report the case of a newborn where delayed diagnosis led to an unnecessary loss of one testicle. Presentation of Case: The newborn was presented one day after delivery with a swollen left blue scrotal pouch. The left testicle was little tender, higher in position and enlarged. Ultrasound revealed a globular, enlarged testicle left, showing hypodense necrotic areas within. Doppler sound could not detect any perfusion of the spermatic vessels. Scrotal fluid was present bilaterally. At operation, the testicle was considered unsalvageable, and left orchiectomy and right orchidopexy were performed. Discussion: In the new-born, it is more than convenient to perfom ultrasound of both testicles at the same time, which allows to compare texture and perfusion easily. Immediate surgical exploration should be performed at any time, even if in diagnostic doubt. The very most important step though is to professionally recognise and to react to this pediatric emergency, as time is of paramount essence. Conclusion: A case of a male newborn with unilateral perinatal testicular torsion is presented, where typical clinical signs and ultrasound features can be seen. Early exploration with orchiectomy of the necrotic testicle and orchidopexy of the healthy side may save the endocrine function and fertility.