Tamoxifen is routinely used for treatment of Estrogen-positive breast carcinoma. Approximately, 50% of patients with metastatic cancer will develop resistance to Tamoxifen. In this research, Tamoxifen was combined with the anti-cancer compound Curcumin. Diblock nanopolymer was used to package the new formulation of Curcumin and Tamoxifen. Anti-cancer efficacy of the obtained compound was evaluated in Tamoxifen-sensitive (TS) MCF-7, Tamoxifen-resistant (TR) MCF-7 cancer cells and Fibroblast cells. MTT assay was used to evaluate anti-proliferation and toxicity. Flow cytometry and Annexin-V-FLUOS were used to assay anti-proliferation and induction of apoptosis respectively. Our results indicate that the obtained nano-compound is less toxic to normal cells compared with Tamoxifen alone, and has higher anti-proliferation and pro-apoptotic activity on TS-MCF-7 and TR-MCF-7. The nanopolymer reduces the Tamoxifen toxicity in normal cells and counters the developed resistance to the drug in cancer cells.