Using density functional theory we studied the influence of group 1 and 11 impurities on the bandgap of Cu2O. Our results show that dopants affect the bandgap through geometric and electronic effects. Geometric effects originate from the compression of adjacent Cu–O bonds while electronic effects are tightly connected to changes in the ability to delocalize electrons through 2 electron 3 center bonds. Doping with alkali metals disturbs the delocalization network and therefore results in an increased bandgap. The 2 electron 3 center bonding network is restored by Au and Ag dopants or decreased doping concentrations.