The numbers of IL-27(+) CD4(+) and IL-27(+) CD8(+) T cells have been found to be increased in tuberculous pleural effusion (TPE) as compared with malignant pleural effusion (MPE). The objective of the present study was to investigate whether pleural IL-27(+) CD4(+) and IL-27(+) CD8(+) T cells can distinguish patients with TPE from those with MPE. Paired specimen of pleural fluid and peripheral blood were collected from 35 patients with TPE and 46 MPE. The numbers of IL-27(+) CD4(+) and IL-27(+) CD8(+) T cells were simultaneously determined by flow cytometry. Receiver operating characteristic curve analysis was used to evaluate the capacity of IL-27(+) CD4(+) and IL-27(+) CD8(+) T cells to differentiate TPE from MPE. The sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), positive predictive value (PPV), and negative predictive value (NPV) of IL-27(+) CD4(+) T cells were 94.3%, 93.5%, 14.46, 0.06, 91.7%, and 95.6%, respectively. The sensitivity, specificity, PLR, NLR, PPV and NPV of IL-27(+) CD8(+) T cells were 80.0%, 93.5%, 12.27, 0.21, 90.3% and 86.0%, respectively. The number of IL-27(+) CD4(+) in pleural fluid is a helpful diagnostic biomarker for the diagnosis of TPE, which performs better than that of IL-27(+) CD8(+) T cells.