Known for its brown and yellow coloring, the palm warbler is a small, somewhat stocky songbird. The colors vary between eastern and western subspecies. Eastern adults in their breeding plumage have yellow undersides with brownish gray wings, and a reddish highlight on the tops of their heads, while individuals of the western variety are duller brown overall with more white undersides. Males and females tend to have similar coloration. They have relatively long tails, which they wag up and down almost constantly. 

Palm warblers measure between 4.7–5.5 inches (12–14 centimeters) long, with a wingspan of 7.9–8.3 inches (20–21 centimeters). 

During the breeding season they inhabit forests, bogs and dry pine barrens. They are frequent visitors of fields and pastures during migration and can be found in open areas with patches of trees and shrubby growth in the winter months.

Their average lifespan is unknown. The oldest known individual lived for over 6 years.

Males are known for their buzzy, trilling song. They use this to attract mates and establish territories, sometimes chasing away other males in the process.

Palm warblers forage for insects and berries by searching among the leaves of shrubs or low trees. In the winter months, they forage on the ground.

These birds are active during the daytime. 

Males and female palm warblers pair up during the breeding season but split up afterwards. During seasonal migrations, they may join flocks with different species of birds.

As migratory birds, palm warblers travel northward to their preferred breeding grounds every spring, with males arriving a few weeks ahead of females.

Females build cup-shaped nests out of peat moss and other soft plant materials on the ground or near the base of a tree. They lay clutches of four to five creamy white eggs with brown markings which hatch after 12 days. Both parents help feed the nestlings. After about 12 days, the young fledge the nest.

The breeding grounds in Canada's boreal forests are vulnerable to extractive industries such as peat harvesting, tar sands oil development, logging and climate change. During migration, palm warblers are killed each year when they collide with lighted towers and windows.