Solvatochromic shifts in nitrogen-doped and nitrogen–sulfur-co-doped carbon dots are studied by analyzing absorption, photoluminescence excitation and photoluminescence emission spectra, and their emission lifetimes in two different solvents, protic water (H2O) and aprotic dimethyl sulfoxide (DMSO). We identify three emission bands belonging to the sp2-hybridized core, the edge, and the functional surface groups of carbon dots, as well as surface-attached fluorophores that emit within the edge band energy range. Edge and surface bands show opposite solvatochromic shifts solely depending on the doping heteroatoms. We are able to reproduce emission shifts observed in DMSO by heating CDs in H2O from 7 to 87 °C, when the polarity and hydrogen-bonding strength of the solvent are reduced. Intrinsic edge band transitions are found to be strongly influenced by the solvent polarity, as charge transfer processes dominate. Surface band transitions are found to be influenced especially by hydrogen bonding between the...