Magnetic nanoparticles (MPs) are emerging as powerful and versatile tools for biotechnology, including cancer research and theranostic applications. Stem cell-mediated magnetic particle delivery has been previously recognized as a modality to target sites of malignancies. Here, we propose the use of adipose-derived mesenchymal cells (ADSC) for the targeted delivery of Fe-Cr-Nb-B magnetic particles to human osteosarcoma (HOS) cells and magneto-mechanical actuation (MMA) for targeting and destroying HOS cells. We show that MPs are easily incorporated by ADSCs and HOS cells, as confirmed by TEM images and a ferrozine assay. MP-loaded ADSCs display increased motility towards tumor cells compared with their unloaded counterparts. MMA of MP-loaded ADSCs induces HOS destruction, as confirmed by the MTT and live/dead assays. MMA enables the release of the MPs towards cancer cells, producing a significant decrease (about 80%) in HOS viability immediately after application. In contrast, normal human dermal fibroblasts' (NHDFs) viability exposed to similar conditions remains high, showing a differential behavior of normal and malignant cells to MP load and MMA exposure. Taken together, the method could derive successful strategies for in vivo applications in targeting and destroying malignant cells while protecting normal cells.