MicroRNA-29b () targets numerous important genes that mediate carcinogenesis and tumor development in breast cancer and . The aim of the present study was to determine the clinical significance of expression in primary breast cancer patients. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) of and certain target genes of , such as DNA methyltransferase 3A (), ten-eleven translocation 1 () and thymine DNA glycosylase (), was performed in 94 primary breast cancer samples. Low expression of in primary tumors was significantly associated with poorer disease-free survival (DFS) (P=0.0075) and overall survival (OS) (p=0.0012). Multivariate analysis indicated that expression was an independent prognostic factor for OS [relative risk=15.6 (2.33-348), P=0.0026]. In addition, a significant inverse correlation was identified between the expression levels of and in estrogen receptor-positive breast cancer patients (P=0.027). To the best of our knowledge, this is the first study to investigate the clinicopathological significance of in breast cancer cases and is shown to act as a tumor suppressive microRNA in breast cancer and as a potential marker for recurrence and metastasis in breast cancer patients.