Malignant blue nevi are a rare variant of cutaneous melanoma often associated with metastatic disease and poor prognosis. Information on the treatment of this condition is limited. This case study reports the use of intralesional interferon -alpha2b (IFN-alpha2b) as a salvage option in a male patient with a congenital blue nevus on the right buttock. After initial diagnosis, the primary lesion (lesion 1) was partially resected and the patient received aggressive treatment with radiotherapy and concomitant polychemotherapy (cisplatin, vinblastine, and dacarbazine). However, the lesion progressed and the patient was treated second-line with carboplatin, paclitaxel, and sorafenib. Although this treatment stabilized the primary lesion, at cycle 6, the patient developed a measurable locoregional metastasis (lesion 2). At this stage, the patient was treated with intralesional IFN-alpha2b twice weekly at lesion 2, followed by weekly intralesional IFN-alpha2b therapy to both lesions, which resulted in partial disease regression. Biweekly maintenance therapy with IFN-alpha2b administered to both lesions maintained a partial response (ongoing at 23+ mo) and allowed complete occupational rehabilitation. Thus, intralesional therapy with IFN-alpha2b may be a viable treatment option in patients with locally advanced melanoma who have progressed on prior radiotherapy, polychemotherapy, and/or multikinase antiangiogenic-based therapy.