Wnt/β-catenin signaling underlies the pathogenesis of a broad range of human cancers, including the deadly plasma cell cancer multiple myeloma (MM). In this study, we report that downregulation of the tumor suppressor microRNA miR-30-5p is a frequent pathogenetic event in MM. Evidence was developed that miR-30-5p downregulation occurs as a result of interaction between MM cells and bone marrow stromal cells, which in turn enhances expression of BCL9, a transcriptional co-activator of the Wnt signaling pathway known to promote MM cell proliferation, survival, migration, drug resistance and formation of MM cancer stem cells. The potential for clinical translation of strategies to re-express miR-30-5p as a therapeutic approach was further encouraged by the capacity of miR-30c and miR-30mix to reduce tumor burden and metastatic potential in vivo, in three murine xenograft models of human MM, without adversely affecting associated bone disease. Together, our findings offer a preclinical rationale to explore miR-30-5p delivery as an effective therapeutic strategy to eradicate MM cells in vivo.