Loligo reynaudii has an elongated slender body with long fins and mantle. The left ventral arm is used to store and transfer spermatophores to the female, the distal part of its arm is modified and bearing 44 to 68 tiny outgrowths on the surface that are in rows. Limbs are expanded, with suckers in transverse rows, the median segment of limbs is greatly enlarged, and their horny rings are smooth with 78 mm mantle length. Its eyes are covered with a membrane which is part of the skin covering the head. It has reddish-brown pigment containing light reflecting cells on the head and mantle. When alive, the colour can change from dark red to almost translucent.