The Slender-Woman is a being, female in appearance, with extremely long, slender arms and legs. She also appears to have 4 to 8 long, black tentacles that protrude from her back. Different photographs and enthusiasts disagree on this fact, so it is theorized she can 'contract' these tentacles at will.

She is described as wearing a black suit, strikingly similar to the visage of the notorious Women In Black. As the name suggests, she appears very thin. She is able to stretch her limbs and torso.