One of the largest snakes in Europe the Aesculapian snake can be more than 2 metres long.
Easily recognisable by its long thin body with small pointed head, prominent eyes and round pupils. Uniform back coloring being yellowish-brown, greyish-brown, greyish-black, or olive green and sometimes speckled with a pale underside.
Juveniles can easily be confused with juvenile grass snakes (Natrix natrix), because juvenile Aesculapian snakes also have a yellow collar on the neck that may persist for some time in younger adults. Juvenile Aesculapian snakes are light green or brownish-green with various darker patterns along the flanks and on the back. Two darker patches appear in the form of lines running on the top of the flanks. The head in juveniles also features several distinctive dark spots, one hoof-like on the back of the head in-between the yellow neck stripes, and two paired ones, with one horizontal stripe running from the eye and connecting to the neck marks, and one short vertical stripe connecting the eye with the 4th to 5th upper labial scales.