Congenital neoplasms in calves are uncommon. Hemangiosarcoma, a vascular endothelial tumor, is more common in adult dogs, but rare reports in ruminants predominantly are documented in adult cattle viscera or stillborn calves. The present report is a case of congenital subcutaneous hemangiosarcoma in a live neonatal calf, emphasizing diagnostic and therapeutic strategies. A 40-day-old male calf presented with a large (15 × 17 × 10 cm), firm subcutaneous mass in the ventral cervical region that was evident since birth. Clinical signs included mild fever, tachycardia, anemia, leukocytosis, and rumen acidosis. Also, concurrent mild prognathism was noted. Ultrasonography revealed heterogeneous hypoechoic tissue with anechoic vascular structures and hyperechoic foci. Fine-needle aspiration yielded only blood, prompting surgical biopsy under local anesthesia. Histopathology revealed unencapsulated, blood-filled channels lined by pleomorphic endothelial cells with atypia, mitoses, hemorrhage, necrosis, thrombosis, and intravascular invasion, confirming hemangiosarcoma. Surgical resection was deemed high risk due to the extensive vascularity, size, and adjacency to vital cervical structures. Conservative care (anti-inflammatory drugs, antibiotics, dietary adjustments) was considered. Three months of follow-up showed enlargement of the mass and impaired growth of the calf. To the best of our knowledge, the present case is the first report of congenital subcutaneous hemangiosarcoma in a live calf. Survival without surgical intervention suggests the potential for a less aggressive behavior of this tumor in the neonate calf, whereas the prognosis in the adult cow has been grave. Further research into the etiology, behavior, diagnosis, and management of congenital vascular neoplasms in calves is warranted.