In this paper, a 1D photonic crystal waveguide and a plasmonic compound nano-system are utilized to design a hybrid photonic-plasmonic device for enhancement of light–matter interaction. Strongly localized light waves in a very small volume intensify the optical field, via surface plasmons due to presence of a gold nanoparticle, which interacts with the resonator’s cavity mode while the photonic crystal nanobeam ensures a high temporal confinement. The enhancement factor of light–matter interaction in the hybrid resonator is investigated through the single-atom cooperativity parameters based on numerically obtained results, which is calculated to be 14 as a result of the considerably reduced optical mode volume in the presence of the plasmonic nanoparticle. Additionally, the theoretical models and calculation procedures, presented in this paper, are demonstrated to be pioneering for the fabrication of efficient quantum devices based on hybrid photonic-plasmonic resonators.