Juvenile xanthogranuloma (JXG) is the most frequent form of non–Langerhans cell histiocytosis. We present a case of giant congenital JXG in a 7-week-old boy, who had a firm and incompressible lesion, measuring 3 × 4 cm in diameter, on his right flank. The clinical appearance of the lesion and the ultrasound results suggested a vascular tumor, such as a hemangioma. Histology confirmed a JXG, although there was an absence of Touton cells, which are usually pathognomonic of JXG. In light of these findings, it would be important to include JXG in the differential diagnosis of congenital tumours, particularly vascular lesions.