The European Roller Coracias garrulus is a secondary hole-nesting bird that has largely been considered genetically monogamous, although molecular techniques to confirm this assumption had never been used. Here we test this hypothesis by using 5 years of data from a nest-box population in the south of Spain and 6 microsatellite markers recently tested in the species. Overall, 49 broods containing 176 nestlings were included. The average annual percentage of nests with either extra-pair paternity or extra-pair maternity was 4.6 and 6.4, respectively. No evidence of cooperative breeding was found in the provisioning videos analysed. Our work confirms for the first time that European Rollers are not exclusively genetically monogamous, opening new avenues in the study of the breeding biology of this near-threatened species.