In this work, we investigate the significant interest of chromium-doped spinels (CDS) resulting in their characteristic red photoluminescence (PL) due to the strong crystal field and the octahedral coordination of the Cr3+ ion. An increase in the luminescence efficiency of these CDSs by interaction with plasmon excitation is studied with the objective of more efficient luminescence. We successfully synthesized the CDS using the citrate sol-gel method and metallic nanoparticles (MNPs), using the classical citrate-reduction method. Additionally, we covered the MNPs with silica shells, which were used to modify a surface. The surface-enhanced effect exerted by modified surfaces (MS) with [email protected] and [email protected] core-shell nanoparticles on the PL of two CDS is studied. The silica shell of MNPs is used as a separator between the [email protected] surface and CDS. An enhancement of CDS PL was found for CDS coupled to MNPs with respect to uncoupled CDS. The PL enhancement factor as well as the lifetimes were investigated. The interaction of CDS with MNPs has been investigated, and several factors were found to influence the PL of CDS. The main mechanism explaining the PL enhancement has been proposed. Our better understanding of the surface-enhanced luminescence (SEL) of CDS may lead to further improvement of this kind of system.