We discovered a breeding population of Yellow-bellied Flycatchers (Empidonax flaviventris) during the summer of 2004 in a mountainous area northwest of Fairbanks, Alaska. A minimum of 13 males, all apparently paired, were defending territories in open montane forest with patches of thick alder, birch, and willow. Expanses of similar unsurveyed habitat suggested the possibility of a much larger population. A nest with four eggs provided the first evidence of this species’ breeding in Alaska. We recorded behavior at this nest by 24-hour videotaping during incubation and when nestlings were 1 and 8 days old. The nestlings fledged after 15 days. This information extends the known breeding range of the Yellow-bellied Flycatcher west of Canada for the first time and, with other sites of suspected breeding, suggests the species may have a broader breeding distribution in Alaska, particularly in remote stretches of the Yukon River drainage.