Spanish sparrow
Within its genus, the Iago sparrow has been considered one of the African 'rufous sparrows', a group which also includes species such as the great sparrow ("Passer motitensis"). These birds were usually treated as distinct species until Reginald Ernest Moreau, writing in the 1962 "Check-list of the Birds of the World", lumped the Iago sparrow and the mainland rufous sparrows as the single species "Passer motitensis". This taxonomy was followed frequently until J. Denis Summers-Smith, a world authority on sparrows, argued in the 1980s that the Iago sparrow's many differences in morphology and behaviour, and separation from the other rufous sparrows by about , are sufficient grounds for species status. Studies of mitochondrial and nuclear DNA have since suggested it may be a close relative of the house sparrow and the Spanish sparrow and not the rufous sparrows.