A new feather mite genus Bernierinyssusgen. n. (Analgoidea: Pteronyssidae), associated with endemic Malagasy warblers (Passeriformes: Bernieridae), is proposed based on morphological evidence and DNA sequence data. Within this genus, we detected six mite species, including five new species described here: Bernierinyssus angulatussp. n. from Crossleyia xanthophrys, B. bernieriaesp. n. from Bernieria madagascariensis, B. bifenestratussp. n. from Hartertula flavoviridis, B. randiaesp. n. from Randia pseudozosterops, B. xanthomixissp. n. from Xanthomixis zosterops (type host) and X. cinereiceps, and B. oxylabis (Mironov and Wauthy 2005) comb. n. (transferred from Pteronyssoides Hull). Phylogenetic relationships of these mites were nearly perfectly congruent with those of their hosts, indicating that ancestral Bernierinyssus probably co-dispersed to Madagascar on the common ancestor of Malagasy warblers and then cospeciated with their hosts. Species of Bernierinyssus are well-delimited based on several lines of evidence: morphology (clear among-specific differences in discrete characters), host associations (one mite species per one host species, except for B. xanthomixis), genetic distances (large COX1 barcoding gap between among- and within-species K2P distances: 8.22–12.38% vs 0–2.9%, respectively), and molecular phylogenetics (all species are well-supported, monophyletic clades). Our study suggests that species of the genus Bernierinyssus have evolved slower than their avian hosts or co-associated feather lice. Despite the discordance in the mitochondrial DNA evolutionary rates, speciation events in mites largely corresponded to bird species divergences, resulting in a nearly perfect correlation between mite and bird species richness (Eichler's Rule). The mite B. xanthomixis was associated with two avian species, but still formed two distinct shallow lineages (COX1 distance: 1.65%) separated by the host species. The nearly strict host-specificity pattern found in Bernierinyssus contrasts with that of continental feather mites, which tend to be less host-specific and have nearly equal proportions of single-host vs multi-host species.