Rayleigh is a fun loving and carefree, not unlike Monkey D. Luffy and Gol D. Roger, his former captain. In his past as first mate to Roger, he was serious and strict in matters of crew discipline. He is open and talkative, except when it comes to the mysterious Black or Void Century, however he was willing to tell Nico Robin if she wished, but she declined his offer.
Although former rivals, he and Whitebeard talked about the past nostalgically, he also has great respect for him, as seen when he passed.
Powers and Abilities
As the former first mate of Gol D. Roger, Rayleigh is apparently extremely powerful, possibly one of the strongest characters introduced in One Piece. He has tremendous physical strength as shown when he killed several giant Sea Kings with his bare hands while swimming to Amazon Lily to see Luffy, from across the ocean, even though he said is 'getting old'. Rayleigh is around Whitebeard's age (72 before death).
His partner in business Shakky, said that he is "100 times more powerful then all of you boys", in reference to the Eleven Supernovas.
He works as a coating mechanic , which allows ships to travel underwater to Fish-men island and act as submarines in general (as seen on Whitebeard's ship during the Battle at Marinford). He uses the coating Yaruikiman resin, he is also said to be one of the best.
He is immensely skilled with a sword, although he self proclaimed that he is out of practice. He was able to fight on par against Kizaru.
Rayleigh is one of the few people in the world who can use all three forms of Haki. He is even able to match Admiral Kizaru in battle, and even wound him. His Haoshoku Haki can be focused; he was able to render an entire room unconscious, except for the Straw Hats and Keimi and his crew mate.