Mycobacterium celatum, a slow-growing acid-fast bacillus, is an uncommon cause of human infection, mainly occurring in patients with AIDS. Rarely, infections restricted to the lung and lymph nodes have been reported in immunocompetent hosts. We report herein a case of M. celatum pulmonary infection that mimicked pulmonary tuberculosis in a patient with ankylosing spondylitis. The literature was reviewed and clinical features of eight HIV-negative patients with M. celatum infection are discussed. The clinical presentation of M. celatum is indistinguishable from tuberculosis, especially in patients with a previous history of pulmonary tuberculosis. Proper treatment depends on a definitive identification of this pathogen, which requires 16S rDNA sequencing or mycolic acid high performance liquid chromatography analysis.