Red-eyed vireos have olive-green upperparts and a creamy white chest and belly. The top of the head is slate gray with a black stripe eyestripe bordered by white. The bill is pointed. Juveniles have brown irises, while adults have red irises. They have stocky bodies, bluish-gray legs and relatively short tails. 

Adults are 4.7-5.1 inches (12–13 centimeters) long, and weigh between 0.4-0.9 ounces (12-26 grams). Their wingspan is about 9.1-9.8 inches (23–25 centimeters) long.

Red-eyed vireos live in deciduous and mixed forests, particularly near small canopy openings. Sometimes they inhabits residential areas that have enough large trees. During fall migration, they stop in Gulf Coast pine forests. In the winter they inhabit a variety of areas, from lowland tropical forests to gardens with scattered trees. 

Red-eyed vireos are noteworthy for their large vocabulary of short songs, which they sing tirelessly from the treetops during the nesting season. 

Red-eyed vireos eat mainly insects during the spring and summer months. They eat more seeds and berries during the fall to give them enough energy for their long migratory flight. In their South American wintering range, they include more fruit in their diets.

Males arrive at the breeding grounds about one week ahead of females, claiming their territory through song and driving away other males until a potential mate arrives. They sing for hours on end during this time.

After a nest site is chosen, females weave together a cup-shaped nest out of twigs, grasses, and other plant material, and it is placed between the fork of two tree branches. Females lay between three and five eggs, which hatch after about 11-14 days of incubation. After hatching, the chicks are fed by both parents until they are ready leave the nest.

Their population is currently stable, although they are at risk for habitat degradation and loss in their winter range.

Like many species, their nests are occasionally parasitized by brown-headed cowbirds. In nest parasitism, the parasite species will lay eggs in the hosts' nests when the parents are absent. After hatching, the parents will feed and care for the cowbird babies as if they were their own, often at the expense of the hosts' babies.