The electrical conductivity of thermoplastic composites made of poly(3,4-ethylenedioxythiophene) (PEDOT) particles and poly(ethylene oxide) (PEO) matrices is here investigated, in particular using a manufacturing process based on twin-screw extrusion. PEDOT particles without PSS were first synthesized by oxidative polymerization in an aqueous medium and characterized using various techniques (conductivity measurements, SEM, TGA, laser granulometry, XRD and XPS). The polymerization temperature of PEDOT particles was found to be a crucial factor. A maximal conductivity of 50 S.cm−1 was obtained when synthesized at ambient temperature. Relationships between the polymerization temperature and the structure of PEDOT particles were revealed and discussed. PEDOT particles were then incorporated up to 60 wt% into PEO matrix by twin-screw extrusion to manufacture electrically-conductive PEO/PEDOT thermoplastic composites. Their electrical conductivity increased with the PEDOT content and outstanding electrical conductivities up to 12 S.cm−1 were reached. The electrical percolation of this system was determined and discussed based on morphological studies by SEM and X-Ray tomography. The effect of PEDOT concentration on thermal properties of PEO matrices was also revealed by DSC. This work provides a novel approach for the manufacture of thermoplastic composites with high electrical conductivities using industrial technologies with multiple applicative perspectives, in particular into polymer-based electronics.