Conjugated conducting polymers and carbon nanotubes, both of which possess a conjugated structure of alternating carbon–carbon single and double bonds for the delocalization of π-electrons, are two important classes of electrochemical sensing materials. The combination of carbon nanotubes with conducting polymers or other functional materials (e.g., DNA chains, proteins, metal nanoparticles, carbon fibres) was found to create synergetic effects, that provide the basis for the development of numerous novel sensors with a high sensitivity, good selectivity, excellent environmental stability, and low power consumption. This article reviews recent developments in this exciting new area of electrochemical sensing by presenting the rational strategy of the author’s group in the design and characterization of these new electrochemical sensors based on architectural diversity of the π-conjugated structure.