<p>This study investigates the effects of radiation force due to the rotational pitch motion of a wave energy device, which comprises a coaxial bottom-mounted cylindrical caisson in a two-layer fluid, along with a submerged cylindrical buoy. The system is modeled as a two-layer fluid with infinite horizontal extent and finite depth. The radiation problem is analyzed in the context of linear water waves. The fluid domain is divided into outer and inner zones, and mathematical solutions for the pitch radiating potential are derived for the corresponding boundary valve problem in these zones using the separation of variables approach. Using the matching eigenfunction expansion method, the unknown coefficients in the analytical expression of the radiation potentials are evaluated. The resulting radiation potential is then used to compute the added mass and damping coefficients. Several numerical results for the added mass and damping coefficients are investigated for numerous parameters, particularly the effects of the cylinder radius, the draft of the submerged cylinder, and the density proportion between the two fluid layers across different frequency ranges. The major findings are presented and discussed.</p>