Multifunctional magneto-plasmonic nanoparticles with magnetic hyperthermia and photothermal therapy could kill cancer cells efficiently. Herein, carbon-encapsulated Au/FeO (Au/FeO@C) was fabricated using an enclosed flame spray pyrolysis. The nanostructures, including an FeO core (51.9-55.2 nm) with a decreasing carbon shell thickness and an Au core (4.68-8.75 nm) coated with 2-4 graphite layers, were tailored by tuning the CH content in the reacting gas mixture. Saturation magnetization (33.7-48.2 emu/g) and optical absorption were determined. The carbon shell facilitated the dispersion of Au/FeO and restrained their laser-induced and magnetic field-induced coalescence and growth. Au/FeO@C exhibited excellent magnetic resonance imaging capability (91.4 mM s) and photothermal performance (65.4°C for 0.8 mg/mL Au/FeO@C at a power density of 1.0 W/cm after 300 s near-IR laser irradiation (808 nm)). Moreover, the combined application of photothermal and magnetic-heating properties reduced the required intensity of both laser and magnetic field compared to the intensity of separate situations. Our work provides a unique, intriguing approach to preparing multicomponent core/shell nanoaggregates that are promising candidates for esophageal cancer cell therapy.