Functional surface coatings are a key option for biomedical applications, from polymeric supports for tissue engineering to smart matrices for controlled drug delivery. Therefore, the synthesis of new materials for biological applications and developments is promising. Hence, biocompatible and stimuli-responsive polymers are interesting materials, especially when they present conductive properties. PEDOT-co-PDLLA graft copolymer exhibits physicochemical and mechanical characteristics required for biomedical purposes, associated with electroactive, biocompatible, and partially biodegradable properties. Herein, the study of fibronectin (FN) adsorption onto PEDOT-co-PDLLA carried out by an electrochemical quartz crystal microbalance with dissipation is reported. The amount of FN adsorbed onto PEDOT-co-PDLLA was higher than that adsorbed onto the Au surface, with a significant increase when electrical stimulation was applied (either at +0.5 or −0.125 V). Additionally, FN binds to the copolymer interface in an unfolded conformation, which can promote better NIH-3T3 fibroblast cell adhesion and later cell development.