Y3Al5O12:Ce3+ (YAG:Ce3+) transparent ceramic phosphors (TCPs) are regarded as the most promising luminescent converter for laser‐driven (LD) lighting. High‐quality YAG:Ce3+ TCPs are still urgent for high efficiency LD lighting devices. YAG:Ce3+ TCPs in a vacuum ambience by using nano‐sized raw materials are prepared. Controlling defects by adding nano‐sized MgO and SiO2 simultaneously enables a high transmittance nearly 80%. After annealing in air furthermore, the luminous efficiency is enhanced greatly from 106 to 223 lm W−1, which is the best result reported now for LD lighting. These results demonstrate that the optimizing YAG:Ce3+ TCPs in a fitting strategy will brighten once again in the next‐generation LD lighting. Based on scanning electron microscopy (SEM) coupled with a cathodoluminescence system, defects and Ce3+ distributions in grains are identified directly for the first time. Controlling defects by adding nano‐sized MgO and SiO2 enables a high transmittance of nearly 80%. After annealing in air, furthermore, the luminous efficiency is enhanced greatly from 106 to 223 lm W−1. These results demonstrate that the optimization of Y3Al5O12:Ce3+ transparent ceramic phosphors in a fitting strategy will brighten once again the next generation of laser‐driven lighting.