Traditional cancer-therapeutic modalities such as chemotherapy suffer from the low therapeutic efficiency and severe side effects. The emerging nanocatalytic therapy could in-situ catalyze the endogenous substances into highly toxic species and then efficiently kill the cancer cells, but the lack of high-performance nanocatalysts hinders their broad clinical translation. In this work, we have successfully developed, for the first time, nanosized zero-valence crystalized iron nanoparticles for in-situ triggering nanocatalytic Fenton reaction within tumor microenvironment to produce large amounts of hydroxyl radicals and subsequently kill the cancer cells, which could be further synergistically enhanced by either photonic hyperthermia or magnetic hyperthermia as assisted by these iron nanoparticles acting as photothermal-conversion or magnetothermal-conversion nanoagents, respectively. Especially, the excellent magnetic performance of these zero-valence crystallized iron nanoparticles has achieved both in vitro and in vivo contrast-enhance magnetic resonance imaging for potentially guiding the photonic/magnetic hyperthermia-synergistic nanocatalytic cancer therapy. This work not only provides the new type of iron-based nanoparticles for biomedical application, but also demonstrates the high efficiency of nanocatalytic cancer therapy as assisted by both photonic and magnetic hyperthermia.