Development of therapeutic systems to treat glioblastoma, the most common and aggressive brain tumor, belongs to priority tasks in cancer research. We have synthesized colloidally stable magnetic nanoparticles (D =336 nm) coated with doxorubicin (Dox) conjugated copolymers of N,N-dimethylacrylamide and either N-acryloylglycine methyl ester or N-acryloylmethyl 6-aminohexanoate. The terminal carboxyl groups of the copolymers were reacted with alendronate by carbodiimide formation. Methyl ester groups were then transferred to hydrazides for binding Dox by a hydrolytically labile hydrazone bond. The polymers were subsequently bound on the magnetic nanoparticles through bisphosphonate terminal groups. Finally, the anticancer effect of the Dox-conjugated particles was investigated using the U-87 glioblastoma cell line in terms of particle internalization and cell viability, which decreased to almost zero at a concentration of 100 μg of particles per ml. These results confirmed that poly(N,N-dimethylacrylamide)-coated magnetic nanoparticles can serve as a solid support for Dox delivery to glioblastoma cells.