Recent studies have focused on the potential use of metal-based complexes for the treatment of cancer. However, there are some limitations of metal-based ligands for the treatment of cancer due to their toxic effects. In the present study, a novel bimetallic Cu(II) complex, [Cu2(μ-(C6H5)2CHCOO)3 (bipy)2)](ClO4), has firstly been synthesized and characterized by FT-IR, and X-ray crystallography. Furthermore, Cu(II) complex-loaded solid lipid nanoparticles (SLNs) were initially prepared by hot homogenization method to overcome their toxic effects. After characterization, comparative cytotoxic and apoptotic activities of the complex and Cu(II) complex-SLNs on human breast cancer cells (MCF-7) and human umbilical vein endothelial cells (HUVEC) were determined. Cu(II) complex demonstrated considerable in vitro cytotoxic effects on MCF-7 (p<0.05) and induced apoptotic cell death (88.02 ± 3.95%) of MCF-7 cells. But, the complex has also toxic effects (69.5%) on HUVEC control cells. For this purpose, Cu(II) complex-loaded solid lipid nanoparticles (SLN) were firstly produced, with a distrubution range of 190±1.45 nm to 350±1.72 nm and zeta potentials of -27.4±1.98 mV and -18.2±1.07 mV, respectively. The scanning electron microscopy (SEM) images of SLNs were also obtained. In vitro studies have shown that Cu(II) complex-SLNs help in reducing the side effect of Cu(II) complex (29.9%) on HUVEC control cells. Therefore, metal based complex might potentially be used for cancer treatment through nanoparticle based drug delivery systems.