The present communication deals with the optical/dielectric characteristics of MgNb2O6 + 0.25Zn(0.5)Cd(0.5)S nanocomposite (10-30 nm) mixture. Zn0.5Cd0.5S (size similar to 10 nm) was synthesized by microwave assisted solvo-thermal method. Monophase magnesium niobate (MN) nanoparticles (10-20 nm) were synthesized in a single step by mechanochemical treatment of MgO + Nb2O5 under dry N-2 atmosphere. The nanocomposite, MgNb2O6 + 0.25Zn(0.5)Cd(0.5)S, was prepared by mechanical admixing of MgNb2O6 and Zn0.5Cd0.5S taken in 4:1 molar ratio. The photoluminescence study shows violet, yellow and orangered emissions by the MgNb2O6 + 0.25Zn(0.5)Cd(0.5)S composite. The observed dielectric constant value (epsilon) for MgNb2O6 + 0.25Zn(0.5)Cd(0.5)S is only 4.7, which is similar to 5 times smaller than the epsilon value of MgNb2O6 while a dielectric loss for the composite being closer to zero ensures promising commercial applications. (C) 2017 Elsevier B.V. All rights reserved.