Strongly luminescent copper and indium co-doped CdS quantum dots (CuIn-doped CdS QDs) were synthesized from copper iodide, indium acetate, cadmium oleate, and 1-dodecanethiol as starting compounds in octadecene solvent. We demonstrated that when co-doping with In, Cu ions can homogeneously dope into CdS QDs and exist in the +1 state. The as-prepared doped QDs exhibited photoluminescence (PL) in the range of 590–800 nm, with a maximum fluorescence quantum yield (QY) of 40%. They also exhibited tunable large Stokes shifts from 100 nm to 300 nm via tuning dopant concentrations of Cu and In. Such an extremely large Stokes shift dramatically decreased the self-reabsorption of QDs. Furthermore, the CuIn-doped CdS QDs exhibited excellent thermal stability and lost only approximately 20% of their emission QY when the temperature was increased from 20 °C to 150 °C. These features make these QDs suitable as emitters for application in lighting.