In this article, we discuss the nontuberculous mycobacterial pulmonary disease in a 40-year-old HIV-seropositive female patient. The patient has a history of pulmonary tuberculosis, experienced two years ago. At the time, she was treated successfully with anti-tuberculous therapy. A chest x-ray (CXR) and computed tomography (CT) scan of the chest showed a thin-walled cavitary lesion in the right lung. In addition, the tree-in-bud sign, indicative of airway obstruction, was present on CT imaging. Fluorescence microscopy using auramine staining showed acid-fast bacilli (AFB) in sputum smears on more than two samples. Mycobacterium tuberculosis was not detected in the nucleic acid amplification test in the same sample. The AFB identified were mycobacteria other than tubercle bacilli, i.e., nontuberculous mycobacteria, that cause cavitary lung disease. Culture in liquid media and subsequent molecular analysis showed Mycobacterium avium complex (MAC). The patient is now being treated with a multidrug regimen of antibiotics and has improved, with documented sputum conversion.