Introduction Oral melanoacanthosis is a rare, benign, mucosal pigmentation characterized by rapid growth which may clinically resemble mucosal melanoma. A biopsy is often indicated to confirm this diagnosis and exclude other pathologies. A reactive etiology is suggested, as melanoacanthosis typically presents on trauma prone mucosal sites. Melanoacanthosis often occurs as a solitary lesion, however multifocal lesions have been reported. Histopathologic characteristics include pigment-laden, cytologically benign melanocytes with prominent dendritic processes scattered throughout acanthotic stratified squamous epithelium. Regression of the lesion has been observed following biopsy, surgical removal, and spontaneously. Case Description An 18 year old male presented for evaluation of spontaneous, multifocal oral mucosal pigmentation. The patient's medical history was significant for eczema which was refractory to topical steroid therapy. Extraoral examination revealed multiple eczematous lesions of the skin of the face, neck, limbs and focal involvement of lower lip. Intraoral examination revealed dark brown, well defined, flat pigmentation of the maxillary and mandibular attached gingiva, bilateral buccal mucosae, bilateral retromolar pads, soft palate, and focal involvement of the hard palate. A biopsy of the left buccal mucosa demonstrated classic histopathologic features of melanoacanthosis. He was subsequently referred to dermatology for evaluation and management of eczematous skin lesions. The patient's identical twin brother had no evidence of melanoacanthosis and no eczema. Conclusion Melanoacanthosis is a rare pigmented lesion of the oral cavity that often resolves post biopsy. This entity is rarely multifocal. The preferred term melanoacanthosis is used to highlight the reactive, benign nature of the condition.