Dendropanax pachypedunculatus Idárraga & Lowry (Araliaceae) is described from lowland forest in the Donoso District of Colón Province along the Caribbean slope of Panama. It most closely resembles D. arboreus (L.) Decne. & Planch., from which it can be distinguished by several characters including its larger fruits, thicker primary inflorescence axes and peduncles, and leaves with pinnate (vs. mostly triplinerved) venation. This new species is known from a single collection made within the footprint of a copper mining project. A preliminary risk of extinction assessment using the IUCN Red List categories and criteria indicates that D. pachypedunculatus should be considered Critically Endangered (CR).