AppearanceTwo of Rayleigh's most distinguishing traits are that he typically wears glasses and that the facial hairs on his chin are arranged like stripes across his lower jaw. He also has a scar over his right eye, which he has had for many years. When he was younger, Rayleigh kept his black hair clean cut and had a moderate amount of facial hair. Over the years, as his hair whitened, he let it grow longer and wild. He also grew a beard from his initial striped facial hair.
PersonalityRayleigh is light hearted, casual and fun loving, much like his captain Gol D. Roger was supposed to have been. In the past he was shown to have been intolerable to the antics of the younger members arguing, and took the position of crew disciplinarian very seriously. He, like Whitebeard seems to have enjoyed talking about the past, although he seems reluctant to speak about certain topics like the Void Century. As stated by Shakky, he loves alcohol and women, the latter of which he proved when he saved Keimi from being mistreated by Disco. He prefers to be called "Ray-San".
Abilities and PowersIn his younger days with Gol D. Roger, Rayleigh commanded the rest of Roger's crew as First Mate. He would do several duties while supervising the rest of the crew. Amongst these duties was disciplining the young Buggy and Shanks over their constant arguing about useless things, such as which of the two polar regions is the colder one.
After Gol D. Roger's crew disbanded, Rayleigh became a coating mechanic in Sabaody. He specializes in coating ships with Yarukiman Resin, a process which enables ships to travel to Fishmen Island.
Rayleigh is apparently extremely powerful, possibly one of the strongest characters introduced. Shakky, a business partner of his, vouches for his strength by saying that he's "100 times stronger than all of you boys", referring to the Eleven Supernovas. Indeed, when Vice Admiral Garp was informed Rayleigh may be on Sabaody Archipelago, rather than go straight to the archipelago, Garp told the Marines not to have his men confront him, due to his phenomenal strength. However, Rayleigh himself has admitted that he is not as young as he used to be, and can tire in battle.  Eustass Kid himself stated that Rayleigh was a "legend".
HakiRayleigh is able to utilize "Haki" the same way displayed by Shanks and Luffy. Also, Rayleigh's spirit power can be focused. He is able to render a specific target completely unconscious without the aid of eye contact, nor adversely affect anybody else near the initial target. He disabled an entire room with this power, save for the Straw Hats, Keimi, and Pappug. Rayleigh later commented that the pirates still standing were no ordinary rookies. Only very strong and determined individuals can resist from being knocked unconscious. One of Trafalgar Law's crewmen was very close to being knocked out. Even Law and Eustass Kid were sweating slightly after enduring the blast. Another glimpse of his strength is seen when he seemingly snatches off Keimi's exploding slave collar and tosses it into the air before it could self destruct. Rayleigh also kicked and redirected an attack by Marine Admiral and Logia Devil Fruit user Kizaru. He is later shown to be strong enough to fight Kizaru to a draw. Although, he was starting to get tired due to his more advanced age.
Rayleigh knows the "True History" of the world from his time with Roger. However, he has also stated that, as a pirate crew lacking the intellect of scholars of Ohara's caliber, they may very well have misinterpreted that information.