The Silvery-throated Jay (Cyanolyca argentigula) is a poorly known Neotropical corvid endemic to the Cordillera de Talamanca of Costa Rica and western Panama. In April 2016, we found an active Silvery-throated Jay nest in Chirripó National Park, Costa Rica. Here we provide the first description of the breeding biology of this species, including nest architecture, estimates of incubation and nestling periods, and observations of adults attending the nest. The large cup nest, placement in the crown of a small tree, and breeding phenology are similar to other Cyanolyca species. We observed up to 5 adults associated with this nest, including at least 3 different adults that fed chicks. These observations suggest cooperative breeding at this nest but are also consistent with the possibility of communal breeding. Future studies with color-banded individuals and genetic sampling will be necessary to better understand what seems to be cooperative breeding in the Silvery-throated Jay.