Breast cancer is the most frequent cancer among women and impacts over two million women each year. Although many different types of anticancer agents are available for breast cancer treatment, doxorubicin is one of the most widely used drug. However, doxorubicin related side effects such as heart failure and arrhythmia limit its usage. To overcome this limitation and improve doxorubicin effectiveness, pegylated liposomal doxorubicin formulation Doxil (R)/Caelyx (R) was developed. Although cardiotoxicity related side effects were reduced with liposomal doxorubicin formulations, a superior effect was not obtained and better approaches are still needed. In this study, it was aimed to develop a more effective doxorubicin formulation than Doxil (R) and to evaluate its anticancer activity. In order to achieve this goal, small sized mesoporous silica nanoparticles (MSNs) (similar to 50 nm) were obtained, actively targeted with folic acid conjugation and loaded with doxorubicin. The obtained nanoparticles were fully characterized, conjugation was verified, and pH dependent drug release profile was shown. The nanoparticles' anticancer activity was investigated in detail on the ZR-75-1 and T47-D breast cancer cell lines. Fluorescence microscope and flow cytometry studies revealed that the cellular uptake of doxorubicin could be enhanced with small sized MSNs. Moreover, folic acid conjugation made a tangible contribution to this effect. Additionally, similar results were also obtained in cytotoxicity studies on both cell lines. In conclusion, actively targeted small sized MSNs may be a promising approach to potentiate the anticancer effect of doxorubicin.