Anaplastic large cell lymphoma is a unique diagnostic subcategory of the T-cell lymphomas in the current World Health Organization classification. Representing approximately 3% of adult and 10% to 30% of childhood non-Hodgkin lymphomas, anaplastic large cell lymphoma classically consists of CD30+ large lymphoid cells with abundant cytoplasm and pleomorphic, often horseshoe-shaped or kidney-shaped nuclei. Among the reported nodal and extranodal sites of occurrence, the gastrointestinal tract and central nervous system have rarely been noted. We report a case of primary anaplastic lymphoma kinase-negative anaplastic large cell lymphoma in the brain of a 46-year-old patient with acquired immunodeficiency syndrome. T-cell lineage was confirmed by T-cell receptor gamma chain gene rearrangements using polymerase chain reaction, and extra copies of the anaplastic lymphoma kinase gene of chromosome 2 were demonstrated by fluorescence in situ hybridization analysis. To our knowledge, primary anaplastic large cell lymphoma of the brain has not previously been reported in acquired immunodeficiency syndrome.