In this investigation, polystyrene/polyacrylonitrile/polyindole (PSt/PAN/PIN) ternary composites with various amounts of PSt, PAN and PIN were synthesized using FeCl3 as an oxidant agent by chemical polymerization technique. The formation of ternary composites was assisted by Fourier transform infrared spectroscopy. Morphological studies demonstrated all composite have a smooth surface. The results of thermal gravimetric analysis indicate that incorporation of PIN in composites advances the thermal stability. X-ray diffraction analysis show that the amorphous nature of PIN and its ternary composites. The conductivities of PIN and the PSt/PAN/PIN composites were investigated with a four-probe technique. The conductivity of PIN was found to be 5.0 × 10–3 S cm–1, also the conductivities of the PSt/PAN/PIN composites were determined to 3.5 × 10–4, 7.4 × 10–4, 1.3 × 10–3, 2.2 × 10–3 and 2.8 × 10–3 S cm–1 respectively, with 9, 27, 45, 63 and 81 wt % of PIN.