Aberrant deregulation of microRNA-195 (miR‑195) is associated with tumorigenesis and the development of cancer. However, its expression and function in prostate cancer (PCa) remain to be elucidated. In the present study, we found that miR-195 expression levels were decreased in human PCa samples and were correlated with patient prognosis. miR-195 overexpression inhibited cell proliferation, cell cycle progression and tumorigenesis via directly targeting HMGA1. Downregulation of HMGA1 expression had an effect similar to miR-195 in the PCa cells. In clinical specimens, HMGA1 was overexpressed in castration-resistant prostate cancer when compared with its levels in benign prostate hyperplasia and androgen-dependent prostate cancer, and its expression levels were inversely correlated with overall survival and biochemical relapse-free survival. In summary, our study suggests that miR-195 functions as a tumor-suppressor gene by downregulating HMGA1 and can be used as a potential target in the treatment of PCa.