Facial congenital infiltrating lipomatosis is a rare subtype of hemifacial hyperplasia. Abnormal growth of one side of the face occurs in all tissues of the affected area, particularly adipose tissue. Diagnosis is by exclusion, as the etiology of this condition is unknown. However, some factors associated with it include heredity, chromosomal and neural abnormalities, atypical twinning forms, altered intrauterine environment, endocrine and anatomical dysfunction, functional abnormalities of the vascular and lymphatic systems, and central nervous system disorders. Herein, we report a 15-year-old girl who sought treatment in the Hospital Heliópolis of São Paulo for congenital facial swelling that partially regressed over time. Extraoral examination revealed facial asymmetry with normal color, soft consistency, and non-pulsatile swelling in the left mandibular region. Intraoral examination showed a slight erythematous tongue and soft palate on the left side. Magnetic resonance imaging showed thickening and signal heterogeneity in the fat planes of the left perimandibular and perimaxillary regions, with thread-like vascular structures in between. Magnetic resonance angiography revealed an increase in the left submandibular and parotid glands. Based on her medical history, physical examination results, and imaging studies, the patient was diagnosed with congenital lipomatosis of the face.