Adult slender-billed curlews measured 36 to 41 cm (14 to 16 inches) long, weighed 255 to 360 grams (9 to 13 ounces), and had a wingspan of 77 to 88 cm (30 to 35 inches). They were mostly white with grayish brown streaks and spots. Although there were few size and plumage differences between males and females, females had longer bills. Juveniles possessed a similar feather patterning, but they lacked the heart-shaped spots of adult specimens.