[2] The blue waxbill was formally described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae under the binomial name Fringilla angolensis.

[3] Linnaeus based his description on the "Blue-Belly'd Finch" that had been described and illustrated in 1750 by the English naturalist George Edwards in his A Natural History of Uncommon Birds.

The female is paler than the male and the blue is confined to the rump, tail, head, and upper breast, with the rest of the underparts being buffy brown.

[9] Both sexes build the nest, an oval-shaped structure with a short entrance tunnel on the side, constructed of grass stems and inflorescences and lined with feathers.

Blue waxbills may also re-use the old nests of other birds, such as scarlet-chested sunbird, spectacled weaver or black-chested prinia, sometimes building a new structure on top of the original.