Despite its status as a global biodiversity hotspot there is still much to be discovered about the birds of Madagascar, including a full accounting of species-level diversity and the avifauna’s origins. The Bernieridae is a Malagasy endemic family that went unrecognized by science for decades and unnamed until 2010. This cryptic family has long represented a missing piece of the puzzle of the avian tree of life. We present the first comprehensive phylogeny of Bernieridae in order to examine its diversification history on Madagascar and its place within Passeriformes. In light of recent discoveries of cryptic species-level diversity in Madagascar’s vertebrate fauna, we used broad geographic sampling and integrative taxonomic methods to investigate the potential for cryptic lineages within every known species of the Bernieridae. Our approach combines phylogenomics using ∼4500 loci of ultraconserved elements (UCEs), genetic clustering of thousands of single nucleotide polymorphisms (SNPs), and statistical analysis of morphological variation. These methods yielded the discovery of two unrecognized species in the previously monotypic genus Bernieria, along with new insights into patterns of fine-scale endemism in Madagascar’s humid forests. Our phylogenomic analyses provide conclusive support for Donacobiidae and Bernieridae as sister families, a biogeographically intriguing result given that the former is restricted to the Neotropics. We found a significant decline in the rate of speciation over time on Madagascar, consistent with a model of adaptive radiation. Bernieridae therefore joins the Vangidae as a second avian adaptive radiation on the island of Madagascar. These insights into the evolution of Bernieridae represent a step forward in understanding the origins and diversity of Madagascar’s endemic avifauna.