Highly efficient apoptotic hyperthermia is achieved using a double‐effector nanoparticle that can generate reactive oxygen species (ROS) and heat. ROS render cancer cells more susceptible to subsequent heat treatment, which remarkably increases the degree of apoptotic cell death. Xenograft tumors (100 mm3) in mice are completely eliminated within 8 days after a single mild magnetic hyperthermia treatment at 43 °C for 30 min.