In this research (PANI/CNT) core/shell nanocomposite were synthesized via in situ chemical oxidative seeding polymerization‚ the results of SEM indicated the structure of synthesized nanocomposite. TEM‚ FTIR‚ UV–Vis‚ XRD analyses of samples showed that this nanocomposite is decorated with (Fe‚ Co) oxide nanoparticles. The VSM test of as prepared and annealed nanocomposite exhibited the saturated magnetization of 1.1 and 3.86 emu/g, respectively; the coercivity values were also − 350 and − 110 Oe, respectively. The reflection loss characteristics of (Fe‚ Co) oxide–Pani–CNT core/shell nanocomposite were also investigated with a vector network analyzer‚ in the 8.2–12.4 GHz range (X band). The maximum absorption increases with enhancement of the dispersed nanoparticles percent in polyurethane matrix from 1 to 10%. The value of the maximum reflection loss in the absorption samples with 1 and 10% of nanoparticles is − 2.14 dB at 9.33 GHz and − 7.32 dB at 11.97 GHZ, respectively.