In this paper, a novel junctionless carbon nanotube field-effect transistor (JL-CNTFET) endowed with a split coaxial gate (SCG) is proposed through a rigorous self-consistent simulation. This latter is based on solving self-consistently the Schrödinger and Poisson equations using the non-equilibrium Green's function (NEGF) formalism and the finite difference method (FDM), respectively. It has been found that the suggested SCG JL-CNTFET can exhibit significantly improved switching performance including the off-current, current ratio, intrinsic delay and power-delay product, due to the decreasing of band-to-band tunneling via the split-gate strategy. The obtained results indicate that the proposed SCG JL-CNTFET can be considered as a promising device for the futuristic high-performance integrated circuits intended for low-power and high-speed applications.