Extra-pair paternity is typically rather infrequent in seabirds, as in most other long-lived and socially monogamous birds. Here we report the first paternity study of the little auk Alle alle, a high arctic seabird which raises only a single chick per year. Parentage was determined using three highly polymorphic microsatellite markers. We found that all 26 chicks in our sample were true genetic offspring of their social parents, with an upper 95% confidence limit of 10.88% for the frequency of extra-pair paternity. This level of extra-pair paternity is not significantly different from frequencies reported from the closely related common Uria aalge and Brünnich's guillemots U. lomvia.