The Plain Antvireo is recorded across Central and South America. In Costa Rica, it occurs in the understory of humid mountain forests, and males and females differ in plumage.
Males described in Costa Rica have dark slate-gray sides of the head, a dark olive-gray back, narrow white wing bars, and a pale yellow belly. Females have a rufous-brown crown, olive-brown upperparts, and a pale yellow belly.
It forages for insects in the understory and at edges of humid forest. Costa Rican records describe pairs or family groups, sometimes joining mixed-species flocks.
An extinction-risk assessment has not been added yet.