Background and Objective: Cancer is one of the most serious diseases. Doxorubicin is a type of chemotherapy drug used to treat a variety of cancers. Doxorubicin is a type of chemotherapy drug used to treat a variety of cancers. However, its side effects have limited its use. The aim of this study was to synthesize and evaluate polymer micelles containing doxorubicin and evaluate its toxicity on MCF7 breast cancer cells and HepG2 liver cancer cells. Material and Methods: For this purpose, PBMA-b-POEGMA diblock copolymer was first synthesized using the RAFT method and confirmed by GPC. Dynamic light scattering (DLS) and Transmission electron microscope (TEM) were used to observe the morphology, size, and polydispersity of the micelles. In addition, in vitro cytotoxicity of DOX-loaded polymeric micelles against MCF7 cells and HepG2 cells were assessed. Furthermore, cell uptake and apoptosis assay of DOX-loaded polymeric micelles against MCF7 cells were evaluated. Results: The TEM image revealed that the nanoparticles were spherical and uniform. The particle size and polydispersity measured by DLS were 35 nm and 0.13, respectively. The drug encapsulation efficiency and drug loading contents were 50±3.46 % and 4.53±0.29 %, respectively. The drug release rate was reported 69% in saline phosphate buffer (pH 7.4) within 24 hours. The results showed that micelles containing doxorubicin had a greater effect on MCF7 cell viability than the free drug. The MTT assay demonstrated that micelles were biocompatible to HepG2 cells while DOX-loaded micelles showed significant cytotoxicity. The IC50 of doxorubicin-loaded micelles against MCF7 cells were obtained to be 0.5 μg/ml. It was further shown that micelles containing doxorubicin had higher cell uptake and apoptosis than free drugs on MCF7 cells. Conclusion: These polymeric micelles are an ideal candidate to deliver anticancer agents into breast cancer cells.