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Abstract The discovery of bivalved sea slugs in the family Juliidae revolutionized our understanding of shell evolution in molluscs. However, relationships among lineages remain unclear, with generic names shared by extant and fossil taxa. Juliidae provide important fossil calibration points for dating phylogenies and for understanding the convergent evolution of a bivalved shell. Here, we present a revision of the systematics and classification of members of the Juliidae including Recent and fossil taxa by integrating molecular data from five genes, geometric morphometrics, and anatomical data. A list of all juliid taxa previously described is provided, along with diagnoses and remarks on genus-level names. Results from a geometric morphometric analysis support a new classification scheme, in which the genus Berthelinia, previously used for Recent and fossil taxa, is restricted to fossil species, and the genera Julia and Edenttellina are used exclusively for Recent species. Species of Edenttellina supported by molecular analyses are illustrated and anatomical details provided, including examination of protoconchs, radular teeth, and reproductive structures by scanning electron microscopy, along with illustrations of existing type material. Distinct biogeographical patterns in Julia and Edenttellina are discussed in the context of ecological differences between these two taxa, including host specificity and developmental mode.