In recent years, light-emitting Mn2+-doped nanocrystals (NCs) have been widely studied because of their strong and stable Mn(2+)d-d emission. Herein, highly efficient colloidal Mn2+-doped Cd-In-S NCs were prepared by a hot injection strategy. The as-prepared NCs have a cubic crystal structure of CdS host and exhibit strong Mn(2+)emission. The photoluminescence (PL) intensity, PL position, and PL lifetime of this Mn(2+)emission can be adjusted by changing the doping level of Mn2+. In particular, by tuning the amount of dopant, the emission color can be varied in the range of 601 nm to 643 nm, which is due to the coordination field environment of Mn(2+)ions changed by the doping concentration. The PL intensity of Mn(2+)is significantly enhanced by the ZnS shell coating, and the highest PL quantum yield can reach 56%, which is attributed to the removal of NCs surface-related defects by shell modification. A prototype LED was fabricated as well by using the as-prepared highly efficient Mn2+-doped Cd-In-S NCs as a color conversion material. The Mn2+-doped multicomponent semiconductor NCs reported here extend the availability of classical Mn2+-doped luminescent materials and provide alternatives for other applications requiring orange-red colloidal NCs.