The creamy-bellied gnatcatcher is long and weighs approximately. The male has a bluish-black cap and whitelores and supercilium. Its upperparts are dark slate blue. Its long tail's central feathers are black and the outermost white with those between being black and white. Its cheeks and underparts are pale yellowish transitioning to white on the lower belly. The female and juvenile are similar to the male but with slate gray crowns.
The creamy-bellied gnatcatcher's diet is not well known but is probably small insects and spiders. It forages by gleaning and hover-gleaning foliage, alone and in mixed-species foraging flocks.
Breeding
Almost nothing is known about the creamy-bellied gnatcatcher's breeding phenology. One nest has been described. It was built by both sexes of moss and leaves in the crotch of a branch near the top of a high tree.
Vocalization
The creamy-bellied gnatcatcher's song is "a simple, rather fast repetition...tee tee tee tee swee swee swee" . Its call is spie .
Status
The IUCN has assessed the creamy-bellied gnatcatcher as Least Concern is 2023, an improvement from its previous assessment of Near Threatened. "This species is restricted to lowland forest in a region where habitat destruction has been widespread...and existing populations are likely to be highly fragmented."