Ulquiorra is a slender, yet fairly muscular, male Arrancar of average height with a melancholic appearance, fairly short, messy black hair, pale white skin, a black upper lip, and green eyes with small slit-shaped pupils similar to a cat's. Part of his bangs falls between his eyes, and he has distinctively thick eyebrows. He has teal lines that descend from his eyes, making it appear as if he is crying. His facial expression rarely changes, and he is almost always frowning. He wears typical Arrancar clothes: a white jacket, black sash, and a white hakama. However, his jacket seems to have longer coattails than others, and the collar is rather high.
Like most other Arrancar, he possesses remnants of his former life as a Hollow in his appearance. His Hollow hole is located on his sternum, though initially, the hole was located on the base of his throat, a change that was seen in both the manga and anime. The remainder of his Hollow mask lies on top of his head, forming a broken horned helmet. He is the fourth-ranked Espada, signified by the tattoo on the left side of his chest.

As a Hollow, Ulquiorra was roughly the same size, with a full white mask and body and large black wings mounted on his lower back. His mask covered his entire face with a line running up the middle which diverged into three near the top of his head. From ear level, two horns sprout out.