The field of bioelectronics leverages the optoelectronic properties of synthetic materials to interface with living systems. These applications require materials that are conductive, aqueous processible, biocompatible, and can be chemically modified for biofunctionalization. While conjugated polymers and polyelectrolytes have been reported that demonstrate several of these features, materials that offer each of these properties simultaneously are rare. Here, we developed copolymers of anionic polyelectrolyte poly(4-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-2-ylmethoxy)-butane-1-sulfonic acid sodium salt (PEDOT-S), containing structural units with amine-reactive NHS-esters. The reported PEDOT-NHS copolymers demonstrate water-solubility and electrical conductivities similar to previously reported PEDOT-S, as well as the ability to bind important amine-rich biomaterials. Furthermore, the PEDOT-NHS copolymers were biocompatible and hemocompatible, and therefore show promise for next-generation bioelectronic and regenerative engineering applications.