Amblygobius sphynx has a total of 7 spines and 13-15 soft rays in its
dorsal fins, the
anal fin has a single spine and 13-15 soft rays. The background colour on the body is yellowish brown fading to white on the underside. There are 5-6 dark brown bars with white markings between them on the flanks and there is a row of small, widely separated black spots along the upper back. The first and second dorsal fins are equal in height and the
caudal fin is rounded. The bost scales are
ctenoid while those on the nape, abdomen, and breast are
cycloid. The depth of the body is 3.6 to 4 times the
standard length. The maximum
total length is . ==Distribution==