Meleated immiscible polypropylene/polystyrene (PP/PS) (70/30 V/V%) blends were prepared by using initiator benzoyl peroxide and maleic anhydride as coupling agent through reactive blending in an internal mixer in order to enhance the mechanical properties. Flexural tests (three-point bending mode) of all formulations were performed to evaluate the effects of addition of benzoyl peroxide (BPO) and maleic anhydride (MAH). Flexural strength of meleated PP/PS blends varies from 29.7 to 82.62 MPa (versus 54.76 MPa of PP/PS blends) depending on the concentrations of BPO and MAH, Compatibilization and over-compatibilization behavior were also studied. Furthermore, the formulation of blend with highest flexural strength (82.62 MPa) was selected to prepare compatibilized polypropylene/polystyrene-activated carbon filled blend composites (PP/PS-AC) at different concentrations (2.5 to 12.5 wt%) of activated carbon (AC). It was noticed that the resistivity of compatibilized PP/PS-AC blend composites decrease rapidly from 1014–106 Ω-cm as the AC concentrations increase from 2.5–5 wt%, due to the formation of conductive paths within the blend composites.