Size: L: 25 cm. Wt: Males 75 g. Females 85 g. Males and females are similar in colour, slightly dimorphic in size. This species is seasonally dimorphic. In flight, the Purple Sandpiper has a narrow white wing-stripe and an all-dark tail.

Breeding Adult: crown tawny, streaked with black; back feathers edged with white and buff; breast and flanks white with blackish-brown speckling; belly white; bill long, slender, slightly downcurved, black with orange base; legs orange-yellow

Winter Adult: head, neck, and upper breast dark greyish-brown; back feathers greyish-brown, with grey or whitish edges; flanks streaked and spotted grey-brown; bill and legs as in breeding adult

Juvenile: crown tawny, lightly streaked with black; cheeks and nape buffy grey-brown; chin whitish; back feathers edged with whitish; breast and flanks white with blackish-brown speckling (tends to be sparse on flanks); bill and legs as in breeding adult