Perovskite nanocrystals (NCs) of CsPbBr₃ have gained special attention in optoelectronic applications owing to their photoluminescence (PL) properties. Increasing the photoluminescence quantum yield (PLQY) in these NCs is important for improving their performance and herein, we report the enhancement of quantum yield by up to 37% by incorporation of La³⁺ ions into CsPbBr₃ perovskite NCs. The enhanced PL and improved stability are hypothesized to be due to a steep decrease in nonradiative recombination (NRR) pathways. This is achieved via trapped and stable excitons (strong binding energy) that enhance radiative recombinations, mainly because of the constriction of the crystal lattice and stronger electron–phonon coupling in the contracted octahedra. Passivation of uncoordinated sites also contributes to radiative recombinations. This work provides insights into establishing the structure–property relationship that exists in perovskite NCs via various photophysical processes. The present study also paves a pathway to detect lanthanum by tracking the changes in PL.