In this work, we propose an analytical model for the intrinsic transcapacitances in ultra-thin gate-all-around junctionless nanowire field effect transistors in the presence of confined energy states of electrons. The validity of the developed model is confirmed from deep depletion to accumulation and from linear to saturation, based on the numerical solution of the Schrodinger equation using Technology Computer Aided Design (TCAD) simulations. This represents an important stage toward AC small signal analysis of junctionless nanowire-based circuits.