Graft copolymers formed by anchoring poly(ethylene glycol) (PEG) chains to conjugated polythiophene have been prepared by copolymerizing two compounds: unsubstituted α-terthiophene (Th3) and a thiophene-derived macromonomer having an α-terthiophene conjugated sequence and one Th3 bearing a PEG chain with molecular weight of 2000 as substitute at the 3-position of the central heterocycle (Th3-PEG2000). The grafting ratio of the resulting copolymers (PTh3∗-g-PEG), which were obtained using 75:25 and 50:50 Th3-PEG2000:Th3 weight ratios, is significantly smaller than that of copolymers derived from polymerization of macromonomers consisting of a α-pentathiophene sequence in which the central ring bears a PEG chain of Mw = 2000 (PTh5-g-PEG). The electroactivity and electrochemical stability of PTh3∗-g-PEG is not only higher than that of PTh5-g-PEG but also higher than that of PTh3, the latter presenting a very compact structure that makes difficult the access and escape of dopant ions into the polymeric matrix during the redox processes. Furthermore, the optical π-π∗ lowest transition energy of PTh3∗-g-PEG is lower than that of both PTh5-g-PEG and PTh3. These properties, combined with suitable wettability and roughness, result in an excellent behavior as bioactive platform of PTh3∗-g-PEG copolymers, which are more biocompatible, in terms of cellular adhesion and proliferation, and electro-compatible than PTh5-g-PEG.