<p>Rare-earth co-doped phosphors are gaining prominence for their potential to overcome the limitations of current white light-emitting devices by enabling efficient energy transfer and tunable emission properties. The Ce³⁺-Dy³⁺ co-doped nanocomposite phosphors MgO-La_1-x-yCe_xDy_yAlO₃ (x = 0, 0.009; y = 0, 0.03, 0.05, 0.07 and 0.09) were prepared using citrate assisted sol–gel method. The X-ray diffraction and the corresponding Rietveld refinements were utilized to confirm the face-centered and rhombohedral crystal structures of MgO and LaAlO₃, respectively. Field Emission Scanning Electron Microscopy images equipped with Elemental Dispersive Atomic X-ray spectra and elemental mapping revealed the inhomogeneous grains with uniform elemental distribution while XPS shows the presence of each element in their respective oxidation states. The optical bandgaps of the synthesized nanocomposites were found to range from 5.53–6.04&#xa0;eV. The energy transfer behavior from Ce³⁺ to Dy³⁺ has been extensively investigated via Photoluminescence excitation spectra, emission spectra and time-resolved photoluminescence. The plausible energy transfer mechanism was found to be d–d interlinkages with an energy transfer efficiency of ~ 82% for MgO-La_0.901Ce_0.009Dy_0.09AlO₃ nanocomposite phosphor, which exhibited maximum luminescence. The impact of secondary phase MgO in the nanocomposite on its defect states and optical properties has extensively been explored to study the remarkably enhanced and prolonged luminescence of nanocomposite than its component La_0.901Ce_0.009Dy_0.09AlO₃. Further, assessment of exemplary parameters such as Color Correlated Temperature, chromaticity coordinates, color purity demonstrated its capability as a green to yellow color-tunable cool-phosphor with varying Dy³⁺ contents, reinforcing their suitability for promising applications in various photonic domains.</p>