We categorized and quantified the complete vocal repertoires of breeding adult auklets (Aethiini, 5 species) in their breeding areas to provide a baseline for comparative study of the structure and function of vocalizations within this monophyletic group of seabirds. We recognized 22 call types across species and 3–5 call types for each species. Calls were characterized by one to five frequency modulated, harmonically rich note types arranged sequentially in varied combinations. Frequency attributes varied more than temporal attributes within and across species. Repertoires and display complexity of nocturnal and diurnal species did not differ consistently. We recognized two major forms of vocal display: alternating arrangement of note types (Cassin's Auklet [Ptychoramphus aleuticus] and Parakeet Auklet [Aethia psittacula]); and sequentially graded arrangement of note types (Least Auklet [A. pusilla] and Whiskered Auklet [A. pygmaea]). One species' repertoire (Crested Auklet [A. cristatella]) was composed of a mix of the two forms of display. There were vocal homologies in frequency modulation of notes, arrangement of notes, and note type composition of displays. Our analysis revealed vocal similarities between: (1) two species not normally grouped together (Cassin's and Parakeet auklets); and (2) Whiskered and Crested auklets, which have been suggested previously to be closely related.