This paper describes an extra-pair copulation (EPC) event between two color-banded Sandhill Cranes (Grus canadensis). This is the first documented occurrence of an EPC during the fertile period of Sandhill Cranes. This event adds to the small list of documented EPCs in long-lived bird species with long-term pair bonds. Participating in an EPC may have allowed the female to potentially gain access to a mate with a breeding territory, something she did not have during the previous two breeding seasons. Benefits to the male may have included increasing his reproductive success without having to raise the offspring or evaluating the female as a potential new mate.