It has a prominent brown eye streak and a brown-striped crown, with a buff breast, some white belly feathers, and a conical beak.

The olive sparrow looks similar to the green-tailed towhee but is smaller and lacks a rusty cap.

The olive sparrow does not migrate, and is resident in thickets, chaparral, and undergrowth near forests, from sea level to 6,000 feet (1,800 m).

Males sing unmusical chip notes similar to the swamp sparrow.

The nest is built two to five feet above ground, and is large, made of straws, twigs, bark, leaves, and stems.