Nanoscale lasers are ideal light-signal sources for integrated photonic devices. Most of the present lasers made of dielectric materials are restricted to being larger than half the wavelength of the optical field. Plasmon lasers made from metallic nanostructures can help to break the diffraction limit, yet they suffer from low optical pump efficiencies and low quality factors. Integrating dielectric lasers with plasmonic waveguides to construct hybrid material systems may circumvent these problems and combine the advantages of the two components. Here we demonstrate the nanoscale output of dielectric lasers via photon-plasmon coupling in rationally designed perovskite/silver heterostructures. The perovskite crystals offer the gain and high-Q cavity for low-threshold laser generation, while the embedded silver nanowires (AgNWs) help to output the lasing modes efficiently in the form of surface plasmons. The output coupling can be modulated by controlling the resonant modes of the two-dimensional perovskite microcavities. The results would pave an alternative avenue to ultrasmall light sources as well as fundamental studies of light-matter interactions.