We provide the first description of nest architecture and composition, adult construction behavior, and egg characteristics for the genus Rhytipterna. We provide these data for a nest of the Rufous Mourner (Rhytipterna h. holerythra) found under construction and followed through clutch completion and subsequent failure at La Selva Biological Station, Heredia, Costa Rica. Given the historically labile taxonomic placement of the genus Rhytipterna, our observations provide important additional lines of evidence further supporting its affinity to Myiarchus within the Tyrannidae. We highlight our record of the incorporation of shed reptile skins in the nest lining, only the second instance of this nest character within Tyrannidae outside of the genus Myiarchus. The phylogenetic distribution of this specialized nesting trait suggests the possibility of a single origin near the base of the subclade Tyranninae. Received 29 August 2016. Accepted 30 November 2016.