MicroRNAs (miRNAs) act as oncogenes or tumor suppressors in human cancers. Increasing evidence shows that deregulation of miRNAs contributes to the development and progression of human non-small cell lung cancer (NSCLC). Here, we identified miR-186 as a tumor suppressor in NSCLC, which was decreased in NSCLC. Overexpression of miR-186 significantly inhibited proliferation, migration, and invasion of NSCLC cells. In addition, Rho-associated protein kinase 1 (ROCK1) was identified as a target of miR-186 in NSCLC cells. Restoration of ROCK1 remarkably reversed the tumor-suppressive effects of miR-186 on cell proliferation, migration, and invasion in NSCLC cells. Furthermore, ROCK1 was inversely correlated with miR-186 expression in NSCLC. Collectively, our data indicate that miR-186 functions as tumor suppressor in NSCLC by targeting ROCK1.