Nako is an elderly man, with a wrinkled face, grey hair, and a grey mustache and goatee, along with grey eyebrows. He wears a bandanna with a red cross, a common symbol for medical personnel (which is edited out in the 4Kids dub) and sunglasses. He wears a striped light green and dark green shirt, under a doctors coat with a red cross on the side on the right arm.
After the timeskip, he has a flower patterned shirt and striped shorts, with the same sunglasses, coat, and bandanna.
He seems to be willing to help others, as he is a doctor, and is probably brave, as he joined the others to try and defeat Arlong, even though he knew he was going to die. He seems a bit grumpy, as he was dumbfounded and angry that Luffy did not have a doctor in his crew to treat any serious wounds that they had, such as the wounds of Zoro. He is otherwise a good doctor and very caring of Nami.
He aids the crowd in fighting the Arlong Pirates and later tends the wounds of Zoro, Luffy, Yosaku, and Johnny. Nako grumbled about the crew having no doctor which gave Luffy an idea to find a doctor of their own. He then put the pinwheel tattoo on Nami's left arm to cover her stab scars.