A neutral C₄ cumulene 1 that includes a cyclic alkyl(amino) carbene (cAAC), its air-stable radical cation 1^.+, and dication 1²⁺ have been synthesized. The redox property of 1^.+ was studied by cyclic voltammetry. EPR and theoretical calculations show that the unpaired electron in 1^.+ is mainly delocalized over the central C₄ backbone. The commercially available CBr₄ is utilized as a source of dicarbon in the cumulene synthesis.