The Java sparrow is about 15 to 17 cm (5.9 to 6.7 in) in length from the beak to its tip of tail feathers. Although only about the size of a house sparrow, it may be the largest species in the estrildid family. The adult is unmistakable, with its grey upperparts and breast, pink belly, white-cheeked black head, red eye-ring, pink feet and thick red bill.

In Asia the Java sparrow is most often raised almost from birth by human breeders and owners, and they become very tame and attached to humans. As such, they can be normally kept in relatively small cages, but let out for indoor exercise without their attempting to escape. In captivity, a variety of colourations have been bred, including white, silver/opal, fawn/isabel, pastel, cream and agate (which currently is rare within Europe captive specimens) along with the pied Java sparrow (called the sakura buncho in Japan).