Intimal sarcoma is a highly aggressive and rare malignant tumor of the vascular system. We are reporting this unusual primary tumor of popliteal artery presenting as aneurysm in an infant. We report a case of an 8-month-old girl with the incidental observation of nontender and pulsatile swelling in the right popliteal fossa. An arterial duplex scan and computed tomography angiography revealed an intensely enhancing well-defined lesion (3.2 cm × 2.4 cm) of the popliteal artery suggestive of pseudoaneurysm/aneurysm. The patient underwent exploration of the popliteal artery with excision of aneurysmal sac. On histopathological examination and immunohistochemical staining, findings were suggestive of intimal sarcoma. Postoperative recovery was uneventful. At 1-year of follow-up, patient is clinically stable with no disability and any signs of recurrence or metastasis. Malignancy in peripheral arterial aneurysmal is extremely rare. More empirical evidence is yet required to make the diagnostic and therapeutic protocol to deal with this aggressive tumor of the vascular system.