We report a simple and scalable pyrolytic route for the synthesis of core-shell FeCo(C) alloy nanoparticles displaying very good microwave absorption properties. This process is based on the pyrolysis of nanocomposite of Fe-Co oxide under inert atmosphere. The formation of core-shell structure consisting of FeCo alloy nanoparticles as core and graphite as shell has been established through different techniques viz., X-ray Diffraction (XRD), High Resolution Transmission Electron Microscopy (HRTEM) and Raman Spectroscopy. Magnetic studies revealed that the saturation magnetization (Ms) and coercivity (Hc) of core-shell nanoparticles is ~140 emu/g and ~60 Oe, respectively. A composite of the FeCo(C) core-shell material in nitrile butadiene rubber (NBR) with 50 wt% loading of the former was found to show tunable reflection loss (RL) of >10 dB within frequency range of 8-12 GHz. © 2014 by American Scientific Publishers.