Objective By investigating the effects of miR-379-5p on the proliferation, invasion and metastasis of mouse breast cancer 4T1 cells, we aimed to provide new therapeutic targets for the clinical inhibition of breast cancer proliferation, invasion, and metastasis. Methods After plasmid transfection, 4T1 cells were utilized to detect the expression of miR-379-5p using fluorescence quantitative PCR. While 5-ethynyl-2’ doxyuridine (EdU) cell proliferation and Transwell assays were employed to detect changes in the proliferation and invasion ability of 4T1 cells in each group.The migration ability of 4T1 cells after overexpression and knockdown of miR-379-5p was examined by scratch healing assay. A transplanted tumor model of breast cancer was established in BABL/ c mice, and the effects of overexpressing miR-379-5p on tumor growth and the number and size of lung metastases were observed. Results EdU result showed that knocking down miR-379-5p enhanced the proliferation ability of the cells compared with the control group cells, and miR379-5p overexpression reduced the capacity of breast cancer cells to proliferate (P<0. 05). Transwell and wound healing assays showed that miR-379-5p knockdown enhanced, while miR-379-5p overexpression significantly inhibited, the invasion and migratory ability of breast cancer cells (P<0. 01). An in vivo tumorigenesis experiment with BABL/ c mice showed that miR-379-5p overexpression significantly slowed the tumor growth rate (P<0. 05) and inhibited lung metastasis (P < 0. 01). Conclusions MiR-379-5p plays a role in tumor gene suppression in breast cancer and inhibits the proliferation, invasion, and migration of mouse breast cancer 4T1 cells.