A 4-yr-old, intact male red-handed tamarin (Saguinus midas) was evaluated because of a 6-mo history of an enlarging axillary mass. Diagnostic findings included a positive intradermal tuberculin test, persistent severe leukocytosis, and hyperglobulinemia. A nontuberculous mycobacterium species isolated from the mass was identified as Mycobacterium asiaticum using 16s ribosomal DNA sequencing and high-performance liquid chromatography.