The metastasis of breast cancer is the leading cause of cancer death in women, and the lung is a common location of a secondary tumor that has metastasized from the primary source tumor. In this work, an attempt to simultaneously inhibit the metastasis and growth of tumor by co-delivering Twist shRNA (shTwi) and paclitaxel (PTX) using the conjugate of pluronic P85 (P85) and low molecular weight polyethyleneimine (PEI) (P85-PEI)/D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) complex nanoparticles (PTPNs) was performed on metastatic 4T1 breast cancer cell line and its pulmonary metastasis mice model. The experimental results demonstrated that PTPNs could effectively achieve cellular uptake and RNA interference. The down-regulation of Twist protein resulted in significant inhibitory effect of cell migration and invasion with the inhibition rate of 88.7% and 91.06%, respectively. The IC₅₀ of PTPNs against 4T1 cells was 63-fold lower than that of free PTX. The prolonged circulation and increased accumulation of PTX and shTwi in lung and tumor were observed in in vivo biodistribution. The in vivo antitumor efficacy showed that PTPNs could not only inhibit the in situ tumor growth effectively, but also completely restrict the pulmonary metastasis in 4T1 pulmonary metastatic mice model. Therefore, co-delivering chemotherapy drugs with metastasis regulator by PTPNs to simultaneously inhibit metastasis and growth of tumor could achieve synergistic effect for the effective therapy of metastatic breast cancer.