Although all-inorganic lead halide perovskite nanocrystals (NCs) have attracted great attention, the intrinsic toxicity of lead remains to be resolved. Doped CsBr NCs have recently proved to be a new promising candidate of lead-free NCs, but the low photoluminescence quantum yield (PLQY) and the difficulty in the fine modulation of chrominance are still the current challenges. Herein, environment-friendly Cu doped CsBr (Cu:CsBr) NCs were synthesized with good stability and high PLQY (∼38.8%) by using a facile one-pot colloidal synthesis approach. Moreover, for the first time, Mn was introduced into the Cu:CsBr NCs, resulting in dual-emission from Cu and Mn dopants. By controlling the doping amounts of Mn, the co-doped CsBr NCs with flexibly controlled two emission peak intensities and chrominance could be realized. The current co-doping method can not only realize fine modulation of chrominance but also avoid the instability induced by mixed halide. Finally, as-synthesized NCs can be employed as an efficient color conversion layer for fabricating phosphor-converted LEDs.