Adaptation to specialized diets often requires modifications at both genomic and microbiomelevels. We applied a hologenomic approach to the common vampire bat ( Desmodus rotundus ), oneof the only three obligate blood-feeding (sanguivorous) mammals, to study the evolution of itscomplex dietary adaptation. Specifically, we assembled its high-quality reference genome(scaffold N50=26.9 Mb, contig N50=36.6 Kb) and gut metagenome, and compared them againstthose of insectivorous, frugivorous, and carnivorous bats. Our analyses showed  i ) a particularcommon vampire bat genomic landscape regarding integrated viral elements,  ii ) a dietary andphylogenetic influence on gut microbiome taxonomic and functional profiles, and  iii ) that bothgenetic elements harbor key traits related to the nutritional (e.g. vitamins and lipids shortage) andnon-nutritional challenges (e.g. nitrogen waste and osmotic homeostasis) of sanguivory. Thesefindings highlight the value of a holistic study of both host and microbiota when attempting todecipher adaptations underlying radical dietary lifestyles.