Tuberculous pleurisy is an infectious disease with a poor prognosis needing early diagnosis. The use of appropriate antituberculosis drugs can improve prognosis. However, the diagnosis of tuberculous pleurisy is often challenging in older patients. Decreased activities of daily living (ADLs) may lead to difficulty in performing invasive procedures to make a definite diagnosis of pleural effusion. We report our experience with a 90-year-old female with the chief complaint of dyspnea with massive pleural effusion. We could not perform an intensive investigation for tuberculous pleurisy. Based on the high value of adenosine deaminase (ADA), we tentatively diagnosed tuberculous pleurisy for the large pleural effusion and treated her well with the initiation of four antituberculosis drugs. ADA in pleural effusion is considered effective for diagnosis among dependent older patients. Furthermore, although it is difficult to diagnose tuberculous pleurisy in older patients, starting treatment to sustain older patients’ lives in their homes is crucial.