Law is a slim man of a relatively tall height. He has faint shadows right under his yellow eyes (grey in the anime), and his mouth is usually seen in a smile. He has dark blue hair (black in the anime), a majority of which is obscured, save for his sideburns and small black goatee by the northern-style fur hat that Law wears, which is white and has spots on the bottom and along the rim.
He is seen wearing a black-sleeved and hooded yellow hoodie with his Jolly Roger out on the front of his chest and the sleeves rolled up. Law also sports a pair of jeans with odd markings on both the knee and ankle areas, similar to the ones on his hat, but darker in color, and a pair of dark, pointed shoes. He has a pair of small earrings on each ear.
He has many tribal-style tattoos on his arms; on both of his hands, are letters spelled as D E A T H tattooed in black on each of the back of his fingers. Originally in the manga, his left thumb was not tattooed, with the letter A missing. Later on, all of his fingers were tattooed complete with all five letters. He also has a black cross on the back of both of his hands. On his chest, he has a tribal-style heart tattoo with his Jolly Roger on it. He has simpler heart tattoo on his shoulders and his Jolly Roger tattooed on his back.
As a child, Law had his fur hat and his faint shadows right under his eyes, but wore the uniform for the medical academy he was attending: a blue lab coat with a red tie, dark blue shorts and green shoes; he was holding a scalpel on his right hand and a frog on his left hand, since he was already in training to become a surgeon, with his father being his teacher. After escaping Flevance, Law lost his tie and lab coat, and his shirt underneath became more raggedly, and his shorts have white spots on them. Because of his heritage, he inherited the Amber Lead Syndrome that accumulated throughout the generations of Flevance, which left his skin white until he obtained his cure.
In Oda's depiction of the Supernova post-timeskip, he seems to have lost the fur rim of his hat and replaced it with a thick bill, turning it into a rather spherical hat resembling a Wool Skipper. He also now wears a yellow t-shirt similar in appearance to his old sweatshirt with a black jacket over the shirt. On Punk Hazard, Law wears his post-timeskip hat with a long black coat with his crew's jolly roger along the hem and on the sleeve, as well as the word Corazon on the back. He wears black boots. His goatee has also become somewhat scruffier. His right hand now also has the fingers tattooed.