From 21 April to 11 May 2007, an apparent hybrid male Black x Eastern Phoebe (Sayornis nigricans × S. phoebe) was observed in Loveland, Larimer County, Colorado. The bird's plumage was intermediate between the species, with paler upperparts, darker flanks, and a less distinct border between dark and white on the breast than expected on the Black Phoebe, and darker upperparts, less head/back contrast, and a darker and more sharply demarcated upper breast than expected on the Eastern. Sonograms of the bird's territorial song show numerous characteristics intermediate between the typical songs of the two species. Although the Colorado bird provides the first strong evidence of hybridization in Sayornis, other sightings suggest the Black and Eastern Phoebes may have hybridized on other recent occasions. Range expansions of both species may increase the frequency of hybridization in the future.