The experimental data were taken in the NanoPhotonics Group at the Cavendish Laboratory (University of Cambridge). The dataset is for the journal article, "Efficient generation of two-photon excited phosphorescence from molecules in plasmonic nanocavities". The photoluminescent spectra were taken with an electron multiplying charge-coupled detected (EMCCD) (Andor iXon) and darkfield scattering spectra by OceanOptics spectrometer. For further description of the setup, see the Method section of the manuscript.