Giant congenital melanocytic nevus (GCMN) is a rare birthmark that places patients at an increased lifetime risk of malignant melanoma. Herein, we describe an unusual case of GCMN that was followed up from birth until 5 years of age. A white girl was born, after an uncomplicated gestation, with a large cutaneous ulceration that extended over her entire back and laterally toward the anterior aspect of her trunk to involve the chest symmetrically. Biopsy specimens from several sites indicated GCMN that was centrally ulcerated. The patient was followed up closely, and the denuded area of skin was allowed to heal by secondary intention. By 19 months of age, the ulceration had healed completely. By 5 years of age, the nevus had lightened significantly and the scar tissue within the nevus had softened. The patient developed normally, meeting all milestones. Clinical and histologic examination did not reveal any signs of malignant transformation. The case we describe here delineates an approach to the long-term management of GCMN complicated by a large ulceration.