The effect of magnetic nanoparticles coated with arabinogalactan on the viability of Ehrlich ascites carcinoma (EAC) cells was studied. The nanoparticles were studied by transmission electron microscopy, Mössbauer spectroscopy, IR spectroscopy, and ferromagnetic resonance. A correlation between the proportion of dead EAC cells in suspension and the intensity of the EPR signal of dinitrosyl iron complexes was found. This result may be due to the presence of NO molecules.