Serum microRNAs have been identified as potential cancer biomarkers. However, the detailed mechanism by which expression of microRNAs contributes to the development and diagnosis of NSCLC remains unknown. This study was to identify specific miRNAs for diagnosing or predicting the prognosis of NSCLC patients and their correlation between miRNA expression in tissues and serums. Six matched cancer and noncancerous tissues from NSCLC patients were analyzed by miRNA microarray. Among these, three miRNAs (miR-21, miR-141, and miR-200c) were examined in 70 NSCLC paired samples (cancer, normal tissue, and serum) and 44 serum samples of normal volunteers by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Consisting with the microarray results, the expression levels of miR-21, miR-141, and miR-200c in NSCLC were higher than those in normal tissues. While the level of serum miR-21 was increased in cancer patients as compared with that in normal counterpart, expression of miR-141 and miR-200c showed lower levels in serums from cancer patients. Overexpression of serum miR-21 was strongly associated with lymph node metastasis and advanced clinical stage of NSCLC. Finally, log-rank and Cox regression tests demonstrated that high expressions of tumor miR 21 and miR-200c or serum miR-21 were associated with a poor survival in NSCLC patients. Our results suggest that tumor miR-21, miR-141, miR-200c, and serum miR-21 may be potential novel biomarkers for the diagnosis of NSCLC. In addition, this study, for the first time, identifies a significant role of the tumor miR-200c played in predicting prognosis in patients with NSCLC.