Abstract In this study, polyindole (PIN) and polyindole/polyethylene (PIN/PE) conducting composites, having various amounts of PIN, were synthesized by chemical polymerization using FeCl 3 as an oxidizing agent and taking the ratio of salt:monomer as 3:1. The samples of PIN and PIN/PE composites were characterized by FTIR, UV–vis, TGA, SEM, Gouy scale magnetic susceptibility, conductivity (1.2 × 10 −3 S cm −1 > σ > 1.96 × 10 −6 S cm −1 , at T = 25 °C) and density measurements. FTIR analysis suggested a 2,3-propagation mechanism for PIN formation. The ground milled samples were subjected to particle size analysis by dynamic light scattering (DLS) and a micron-sized particle distribution was obtained. A series of volume fractions ( ϕ = 10–25%) were prepared from the materials in silicone oil (SO) and their sedimentation stabilities determined. The most stable composite [PIN(89%)/PE(11%)] against gravitational sedimentation was subjected to flow-rate measurements under externally applied electric field strength ( E ) and an electrorheological (ER) activity was observed; threshold energies ( E t ) were calculated. The effects of volume fraction, shear rate, external E , frequency and temperature onto ER activities of the suspensions were investigated. Enhancement in the electric field viscosities and shear thinning viscoelastic behaviors were observed for all the samples studied. Recoverable viscoelastic deformations were determined from the creep tests under external E .