Quantum emitters located in proximity to a metal nanostructure individually transfer their energy via near-field excitation of surface plasmons. The energy transfer process increases the spontaneous emission (SE) rate due to plasmon-enhanced local field. Here, we demonstrate a significant acceleration of the quantum emitter SE rate in a plasmonic nanocavity due to cooperative energy transfer (CET) from plasmon-correlated emitters. Using an integrated plasmonic nanocavity, we realize up to sixfold enhancement in the emission rate of emitters coupled to the same nanocavity on top of the plasmonic enhancement of the local density of states. The radiated power spectrum retains the plasmon resonance central frequency and line shape, with the peak amplitude proportional to the number of excited emitters indicating that the observed cooperative SE is distinct from superradiance. Plasmon-assisted CET offers unprecedented control over the SE rate and allows us to dynamically control the spontaneous emission rate at room temperature which can enable SE rate based optical modulators.