A carbonaceous monolith material was produced from polyacrylonitrile@lignin (PAN@lig) composite hybrid; the sensing and adsorption capabilities of the material were evaluated. Because the two carbon-based precursors, PAN and lignin, have different characteristics, the resulting carbonaceous hybrid material was expected to exhibit unique properties. The controlled carbonization of PAN@lig produced a carbonaceous monolith with characteristic external and internal structures. Electron microscopy and cyclic voltammetry analyses of the morphological and electrochemical features of the monolith revealed stable structural and electrochemical properties. The hybrid, which acted as an electrochemical capacitor because of the electrical conductivity of the monolith, was suitable for use as a sensing material. The feasibility of using the carbonaceous monolith as a sensing medium was demonstrated by extensive electrical measurements of a simple sensor geometry. The carbonaceous hybrid also demonstrated the capacity to adsorb toxic chemicals/substances, such as radioactive heavy metal ions. The adsorption behavior was analyzed using several isotherm and kinetic models.