A major cause of cancer related death for women in Australia is breast cancer metastasis. For a tumour to metastasise, it first must invade from the primary tumour, extravasate and survive in the bloodstream and then germinate at a distant site to form a secondary tumour. An important component of this process is epithelial-mesenchymal transition (EMT), characterised by tumour cells losing their epithelial non-invasive properties and gaining mesenchymal properties, including loss of cell–cell adhesions which make them more motile and have the ability to invade. We have recently demonstrated that the miR-200 family play a crucial role in maintaining the epithelial phenotype via repression of the ZEB transcription factors123 . The miR-200 family is divided into two functional clusters miR-141/200a and miR-200b/200c/429, which are clustered depending on their “seed” sequence. The aim of this study is to investigate the individual roles of miR-200 family members in regulating spontaneous breast cancer metastasis using a xenograft animal model. We found that stable over-expression of miR-200b or miR-200c, but not miR-141, in the highly metastatic MDA-MB-231 (LM2) subline, led to a loss of ZEB1 expression and a reduction in the ability of these cells to spontaneously metastasise from the mammary fat pad. In experimental metastasis assays, miR-200b expressing cells did not enhance lung colonisation indicating miR-200b was specifically influencing cell invasion from the primary tumour. Re-expression of ZEB1 in the miR-200b stable cell line could not alleviate metastatic repression, suggesting miR-200b suppresses tumour cell invasion by targeting multiple genes. Together, this data implies that miR-200 family members can differentially regulate spontaneous breast cancer metastasis and can operate through ZEB1-independent pathways.