Poly(o-phenetidine) nanocomposites (PNG) with NiCoFe2O4 and exfoliated graphite have been synthesized via in-situ emulsion polymerization. Systematic investigations reveal that the NiCoFe2O4 nanoparticles (30-40 nm) in the poly(o-phenetidine) matrix have phenomenal effect in determining the electrical, magnetic, and the microwave absorption properties of the nanocomposites. Shielding effectiveness due to absorption (SEA) value of 32 dB (>99.9%) has been achieved for PNG composite for its use as broadband microwave absorbing material. The microwave absorption of these composites can be attributed to dielectric loss from graphite and poly(o-phenetidine) matrix, and magnetic loss from NiCoFe2O4 nanoparticles.