The present work envisages synthesis of magnetic nanocomposites by ion beam mixing technique using swift heavy ion irradiation of Ni-Teflon bilayer system and its magnetic characterizations. The nanocomposite is characterized by Rutherford backscattering spectrometry (RBS), transmission electron microscopy (TEM), scanning probe microscopy (SPM) and superconducting quantum interference device (SQUID) magnetometer. Cross-sectional TEM and magnetic force microscopy (MFM) results confirm the formation of nanocomposite. Magnetic characterizations reveal that nanocomposite exhibits ferromagnetic behavior with an increase in the coercivity, which is attributed to the formation of Ni nanoparticles. The coercivity of the nanocomposite is found to be 112 Oe at room temperature which is two orders of magnitude larger than that of the bulk Ni (0.87 Oe).