There has been a growing interest in applying CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) for optoelectronic application. However, research on doping of this new class of promising NCs with optically active and/or magnetic transition metal ions is still limited. Here we report a facile room temperature method for Mn2+ doping into CsPbCl3 NCs. By addition of a small amount of concentrated HCl acid to a clear solution containing Mn2+, Cs+, and Pb2+ precursors, Mn2+-doped CsPbCl3 NCs with strong orange luminescence of Mn2+ at ∼600 nm are obtained. Mn2+-doped CsPbCl3 NCs show the characteristic cubic phase structure very similar to the undoped counterpart, indicating that the nucleation and growth mechanism are not significantly modified for the doping concentrations realized (0.1 at. % - 2.1 at. %). To enhance the Mn2+ emission intensity and to improve the stability of the doped NCs, isocrystalline shell growth was applied. Growth of an undoped CsPbCl3 shell greatly enhanced the emission intensity of Mn2+ and resulted in lengthening the radiative lifetime of the Mn2+ emission to 1.4 ms. The core-shell NCs also show superior thermal stability and no thermal degradation up to at least 110 °C, which is important in applications.