The Bluish Flowerpiercer belongs to the tanager family Thraupidae, within the diverse subfamily Diglossinae, which consists of 64 species mostly found at high elevations (Burns et al. 2014). There are 14 genera in this subfamily, including the Bluish Flowerpiercer's genus, Diglossa, which includes 18 species (Burns et al. 2014). DNA analysis strongly supported Catamenia as sister to the genus Diglossa (Burns et al. 2014). Although the Masked Flowerpiercer has sometimes been placed in the genus Diglossopis, Mauck and Burns (2009) found this genus to be non-monophyletic and thus its use is unwarranted. Vuilleumier (1969) subdivided Diglossa into 4 species groupings mostly based on physical features, with the Bluish Flowerpiercer placed in the caerulescens group alongside D. cyanea, D. glauca, and D. indigotica due to the shared characteristics of blue plumage, poorly marked sexual dimorphism, and relatively unspecialized bills. These four species made up the genus Diglossopis; recent phylogenetic analyses of DNA sequence data have established this grouping as non-monophyletic due to the position of the Indigo Flowerpiercer (D. indigotica). The Bluish Flowerpiercer is sister taxa to the Masked Flowerpiercer (D. cyanea), with strong support. These species form a clade which is the sister taxon to the Deep-blue Flowerpiercer (D. glauca) (Mauck and Burns 2009, Burns et al. 2014).