Multidrug resistance (MDR) of tumor cells is a major obstacle to the success of cancer chemotherapy. Poloxamers have been used in cancer therapy to overcome MDR. The objective of this research is to test the feasibility of paclitaxel-loaded poly(epsilon-caprolactone)/Poloxamer 188 (PCL/Poloxamer 188) nanoparticles to overcome MDR in a paclitaxel-resistant human breast cancer cell line. Paclitaxel-loaded nanoparticles were prepared by a water-acetone solvent displacement method using commercial PCL and self-synthesized PCL/Poloxamer 188 compound, respectively. PCL/Poloxamer 188 nanoparticles were found to be of spherical shape and tended to have a rough and porous surface. The nanoparticles had an average size of around 220nm, with a narrow size distribution. The in vitro drug release profile of both nanoparticle formulations showed a clear biphasic release pattern. There was an increased level of uptake of PCL/Poloxamer 188 nanoparticles (PPNP) in the paclitaxel-resistant human breast cancer cell line MCF-7/TAX, in comparison with PCL nanoparticles. The cytotoxicity of PCL nanoparticles was higher than commercial Taxol in the MCF-7/TAX cell culture, but the differences were not significant. However, the PCL/Poloxamer 188 nanoparticles achieved a significantly higher level of cytotoxicity than both of PCL nanoparticle formulation and Taxol(R), indicating that paclitaxel-loaded PCL/Poloxamer 188 nanoparticles could overcome MDR in human breast cancer cells and therefore could have considerable therapeutic potential for breast cancer.