Objective: To investigate the miR-26b expression and its influence on the biological behaviors in breast cancer cells. Methods: The differences of miR-26b expressions in normal breast cell line MCF-10A and breast cancer cell line MCF-7 were compared. Using untreated MCF-7 cells as blank control, the changes in miR-26b expression, abilities of proliferation, migration and invasion, and Foxf2 mRNA and protein expressions in MCF-7 cells after transfection with miR-26b mimics (miR-26b) group or empty plasmid (negative control group) were determined. The influence of miR-26b on transcriptional activity of Foxf2 in MCF-7 cells was determined by dual-luciferase reporter assay system. Results: The miR-26b expression level in MCF-7 cells was significantly lower than that in MCF-10A cells (P<0.05). In miR-26b group compared with the blank control group or negative control group, the miR-26b expression level was significantly increased, the abilities of proliferation, migration and invasion were significantly decreased, and the mRNA and protein expression levels of Foxf2 were significantly down-regulated (all P<0.05). The transcriptional activity of Foxf2-3'UTR was significantly inhibited in MCF-7 cells after miR-26b mimics transfection (P<0.05). Conclusion: MiR-26b expression is decreased in breast cancer cells, increasing its expression can suppress the malignant biological behaviors of breast cancer cells, and the mechanism may be related to its down-regulating Foxf2 expression.