Hylaeus Fabricius (Hymenoptera, Colletidae) is a genus of bees that can be readily recognized by the relatively hairless black bodies with yellow maculations (markings) on the face and thorax, including the legs. However, species-level identification is difficult due to the maculations of many species being highly variable with respect to shape and size, often resulting in high degrees of similarity between and among species. I use a combination of morphological and genetic (using the 558bp COI sequence – the barcode gene) analyses to assess species richness and diversity for the Hylaeus found within Canada, and create a comprehensive checklist and key to the species. By combining these two approaches, we now have a better understanding of Canada’s bee fauna: 1) species richness is likely to be much higher in Hylaeus, with many morphologically distinct specimens representing unique molecular taxonomic units (MTOs) (corresponding to Barcode Index Numbers, or BINs) not matching previously published species descriptions; 2) H. mesillae and H. modestus, both species with many synonyms each, are likely multiple cryptic species; 3) validation of the species H. gaigei was accomplished through the discovery of the male (genetic match to female) that can be distinguished from morphologically similar species; 4) previously unknown morphological variable forms were found in several species, including H. gaigei, and H. mesillae; 5) based on specimens examined here, previous records of H. nevadensis and H. rudbeckiae in Canada may be due to misidentification; 6) the phylogenetic relationships of species and subgenera occurring in Canada are better understood, with genetic analyses supporting pre-established morphological characters used to assign species to their respective subgenus.