We describe the case of a 5-year-old boy with an idiopathic popliteal artery aneurysm on the right leg, who presented the first clinical manifestations from the age of 3 months, with an increase in the circumference of the right lower limb, visible superficial venous system and purplish coloration, without compromised mobility. A final imaging diagnosis was made when patient was 2 years old, through computed tomography angiography, with subsequent surgical repair at 5 years by popliteal-popliteal bypass (supra-infra patellar), bypass bridge with reversed greater saphenous vein, anastomosis with continuous stitches, proximal, and distal ligation of the aneurysm. Patient evolves satisfactorily in the post-operative period.