The Sharp-tailed Sandpiper is a medium sized wader with a straight black bill that has an olive-grey base. It has a chestnut crown and nape, a white eyebrow, and reddish brown upperparts, with each feather having a black centre. The rump and tail are black, with white outer margins visible in flight. The wings have an indistinct white bar. The breast and flanks are white, streaked and speckled black, with a reddish brown tinge on the chest, grading into a white belly and undertail. The legs are olive. This species is commonly seen with other waders during its migration from northern breeding grounds.