The adult gray kingbird is an average-sized kingbird. It measures 23 cm (9.1 in) in length and weighs from 37 to 52 g (1.3 to 1.8 oz). The upperparts are gray, with brownish wings and tail, and the underparts are white with a gray tinge to the chest. The head has a concealed yellow crown stripe, and a dusky mask through the eyes. The dark bill is heavier than that of the related, slightly smaller, tropical kingbird. The sexes are similar, but young birds have rufous edges on the wing coverts, rump and tail.
This tyrant flycatcher is found in tall trees and shrubs, including the edges of savanna and marshes. It makes a flimsy cup nest in a tree. The female incubates the typical clutch of two cream eggs, which are marked with reddish brown.
Gray kingbirds wait on an exposed perch high in a tree, occasionally sallying out to feed on insects, their staple diet.
Like other kingbirds, these birds aggressively defend their territory against intruders, including mammals and much larger birds such as caracaras, red-tailed hawks and broad-winged hawks.