The development of multidrug resistance (MDR) remains a major limitation to successful chemotherapy in osteosarcoma. Preventing the introduction of MDR has been a research hotspot in clinical and investigational oncology. The aim of this study was to evaluate the preventive effects of tetrandrine (TET) against MDR in osteosarcoma. For this purpose, U-2OS human osteosarcoma cells were treated with paclitaxel alone or a combination of paclitaxel with TET. The cells treated with paclitaxel alone eventually acquired MDR along with the overexpression of and highly activated P-glycoprotein (Pgp), while the cells treated with the paclitaxel-TET combination were sensitive to chemotherapeutic drugs and expressed decreased levels of Pgp and less Pgp activity. The promoter activities of MDR gene 1 (MDR1) and nuclear factor (NF)‑κB, and the expression levels of NF-κB and p-IκB-α were all enhanced in the cells cultured with paclitaxel alone. NF-κB DNA-binding activity and the binding ability of NF-κB to the MDR1 promoter were also enhanced in the cells cultured with paclitaxel alone compared to the control cells. However, the expression and activity of NF-κB were significantly decreased in the paclitaxel-TET combination-treated group as compared with the cells treated with paclitaxel alone. On the whole, our findings suggest that TET prevents paclitaxel-induced MDR by inhibiting Pgp overexpression through a mechanism that may involve the inhibition of NF-κB signaling in osteosarcoma.