Accumulated evidence indicates that aberrant microRNAs (miRNAs) expression plays an important role in the initiation and progression of various cancers, including breast cancer. Previous studies suggested that miR‑139‑3p might serve as a tumor suppressor and is downregulated in several cancer types. However, the expression patterns and exact role of miR‑139‑3p in breast cancer remain to be elucidated. In this study, we aimed to analyze the effect of miR‑139‑3p on the progression of breast cancer and the mechanism involved. Through bioinformatics analysis and in vitro experimental studies, we found that miR‑139‑3p was decreased in breast cancer tissues and cell lines, and decreased miR‑139‑3p is associated with a poor prognosis in breast cancer patients. Overexpression of miR‑139‑3p by transfection significantly inhibits cell proliferation, migration, and invasion of breast cancer cells. Bioinformatics analysis and luciferase reporter gene assay confirmed that RAB1A was a potential target of miR‑139‑3p. Furthermore, overexpression of RAB1A counteracted the suppressing effects of miR‑139‑3p on breast cancer cell migration, invasion and epithelial‑to‑mesenchymal transition (EMT). Taken together, these data suggest that miR‑139‑3p plays a tumor suppressive role in breast cancer by targeting RAB1A and may serve as a potential new biomarker for breast cancer prognosis.