Phonon transmission across a solid–vacuum–solid nanogap can be induced by thermal resonance owing to the quasi-Casimir coupling between interfacial solid layers. However, the thermal energy transport across the nanogap with the existence of adsorbed liquid layers on solid surfaces is still not well understood. Here, the thermal resonances between adsorbed liquid layers were investigated using the classical non-equilibrium molecular dynamics simulations. The existence of thermal resonance between the solid–solid or liquid–liquid interfacial layers separated by the vacuum nanogap was verified through the analyses of the atomic vibrational displacements and the vibrational density of states.