The aim of the present work was to search for identification of novel reactive oxygen species (ROS) scavengers by testing new fused chromenopyrimidinethiones, which was synthesized using Fe3O4 nanoparticles. The new compounds were also tested for their cytotoxic activity. The obtained results showed that the incorporated pyrimidinethione moiety significantly increase antioxidant activity. In conclusion, the study of the pharmacological properties of the new chromenopyrimidinethiones allowed establishing new structure–activity relationships for splitting antioxidant and cytotoxic activity of these compounds.