We have synthesized an electro-active amphiphilic copolymer with carbazole side chains via free radical polymerization using 7-(4-vinylbenzyloxy)-4-methyl coumarin and 9-(4-vinylbenzyl)-9H-carbazole as the monomers. The copolymer can self-assemble to form micelles (termed EACMs) in aqueous solution and can adsorb onto the surfaces of MWCNTs via π–π interactions and thereby cause the efficient dispersion of the MWCNTs in aqueous solution. The coumarin groups in the copolymer undergo UV-induced photo-crosslinking, which further improves the stability of the suspension. Moreover, the electro-active carbazole moieties in the EACMs can undergo electropolymerization to form a conducting network on the MWCNTs that significantly accelerates electron transfer. The EACM/MWCNTs hybrid was applied to the amperometric sensing of dopamine (DA) as a model analyte. After electropolymerization, the electrode exhibited good sensitivity and selectivity toward the determination of dopamine with a 0.2 μM detection limit and a wide linear range. The method described here provides a viable route to water-dispersible and stable carbon nanotubes while preserving their outstanding electrical properties. We presume that the composite described here represents a valuable tool for the construction of electrochemical sensors and electronics.