Modulation of the level of reactive oxygen species (ROS) has been a promising therapeutic strategy in the field of cancer therapy. For this reason, elevating intracellular ROS production by exogenous ROS generators may be an efficient approach to selectively kill cancer cells. In this work, we report on mineralized polymeric nanoparticles as novel oxidative stress amplifying anticancer agents. Upon endocytosis, the nanoparticles can increase the level of hydrogen peroxide (H₂O₂), and through the Fenton-like reaction, they can subsequently catalyze the conversion of H₂O₂ into highly toxic apoptosis-inducing hydroxyl radicals (·OH). The mineral species associated with this oxidative stress enhancing process would maintain its dormant crystalline structure at physiological pH, while, at endosomal pH, it would dissolve into ionic elements to induce the ROS stress. This mineralized nanoparticle would serve as a novel ROS-modulating anticancer agent.