Mycobacterium celatum is a recently described organism. Herein we describe a case of M. celatum lymphadenitis in an immunocompetent child and the first reported case of a M. celatum infection (lung abscess) in a transplant recipient. A literature review identified 19 other cases of M. celatum infection. Fifteen occurred in patients with the acquired immunodeficiency syndrome. Of these, nine were disseminated and six were localized (primarily to the lungs). The remaining 4 patients were immunocompetent and had localized infection (pneumonitis or lymphadenitis). Diagnosis of M. celatum infection can be challenging as M. celatum can cause false-positive results with the current version of the Amplified Mycobacterium tuberculosis Direct Test (Gen-Probe, San Diego, CA.). Definitive identification is available by DNA sequencing or high-performance liquid chromatography. M. celatum can cause infection in immunocompromised and immunocompetent hosts.