The monodispersion of magnetic nanoparticles in conducting polymer is the prerequisite to make a high quality composite for tunable electromagnetic interference (EMI) shielding. To meet this challenge, we have designed and synthesized ferrofluid based nanoarchitectured polypyrrole composites containing Fe3O4 (8-12 nm) via in situ oxidative polymerization. To tune the microwave signals, polypyrrole composites (PFF) with different monomer/ferrofluid weight ratios have been prepared and characterized in microwave frequency domain. A maximum shielding effectiveness value of SEA(max)) = 20.4 dB (similar to 99% attenuation) due to the absorption of microwave has been observed in the frequency range of 12.4-18 GHz and attenuation level varied with ferrofluid loading. The electrical conductivity of PFF composite is of the order of 10(-2) S cm(-1) order and having superparamagnetic nature with saturation magnetization (M-s) of 5.5 emu g(-1). The lightweight PFF composites with high attenuations can provide full control over the atomic structure and are favorable for the practical EMI shielding application for commercial electronic appliances. (C) 2013 Elsevier B.V. All rights reserved.