Emerging evidence shows that microRNAs (miRNAs) play an important role in pathogen-host interactions. Circulating miRNAs have been repeatedly and stably detected in blood and hold promise to serve as molecular markers for diverse physiological and pathological conditions. To date, the relationship between circulating miRNAs and active pulmonary tuberculosis (TB) has not been reported. Using microarray-based expression profiling followed by real-time quantitative PCR validation, the levels of circulating miRNAs were compared between patients with active pulmonary tuberculosis and matched healthy controls. The receiver operating characteristic curve was used to evaluate the diagnostic effect of selected miRNA. Bioinformatic analysis was used to explore the potential roles of these circulating miRNAs in active pulmonary tuberculosis infection. Among 92 miRNAs significantly detected, 59 miRNAs were downregulated and 33 miRNAs were upregulated in the TB serum compared to their levels in the control serum. Interestingly, only two differentially expressed miRNAs were increased not only in the serum but also in the sputum of patients with active pulmonary tuberculosis compared to the levels for the healthy controls. Upregulated miR-29a could discriminate TB patients from healthy controls with reasonable sensitivity and specificity. A number of significantly enriched pathways regulated by these circulating miRNAs were predicted, and most of them were involved in acute-phase response, inflammatory response, and the regulation of the cytoskeleton. In all, for the first time our results revealed that a number of miRNAs were differentially expressed during active pulmonary tuberculosis infection, and circulating miR-29a has great potential to serve as a marker for the detection of active pulmonary tuberculosis infection.