Two new locations, vocalizations, and the nest of the little known Selva Cacique (Cacicus koepckeae, Icteridae) are described from southeastern Peru. Similarities between the vocalizations of Selva and Ecuadorian caciques (C. sclateri) indicate that the two species may be closely related. The Selva Cacique may be ecologically restricted to narrow rivers and headwater regions, where found in river margin habitats and nearby transitional forest. Its occurrence from an elevation of 300 m at the type locality to ≤575 m at the headwaters of the Río Manu Chico, 240 km from the type locality, indicates that it may occur in small numbers over a much larger area than was previously known.