Sepia hedleyi is a relatively small species of cuttlefish with a mantlelength of 83 mm in males and 102 mm in females. It is beige in colour lacking any markings on the arms. There are longitudinal rows of up to 6 ridge-like bumps forming ridges along each side, next to the base of each fin which vary in colour from orange to pink. The tentacular club is crescent-shaped and has a flattened surface which bears 9 to 12suckers in transverse rows. The fins are widest in their posterior third, rounded at their posterior ends where there is a narrow separation between the fins. The cuttlebone is oblong.