Kaido is a merciless and confident warrior who never misses an opportunity to gain an advantage in war, as evidenced by his plan to attack Whitebeard during the latter's attempt to save Portgas D. Ace from execution. He apparently craves excitement, as he is prepared to start the largest war in the world because he felt it was too mundane. This recklessness, coupled with his apparent inability to die, has caused Kaido to make attempting suicide his hobby.
He is also pitiless and not open to negotiations or excuses, making it unwise to provoke or underestimate him; this is enforced dramatically when Donquixote Doflamingo, a former Shichibukai and former World Noble known for his fearless attitude, was very afraid of angering Kaido when he became potentially unable to fulfill his end of their business deal due to Trafalgar D. Water Law holding Caesar Clown hostage. One of his crewmates later stated that Kaido would be very angry once he heard the news of the SMILE Factory's destruction.
Kaido is highly confident in his power and considers himself to be far above the likes of Supernovas, referring to their actions as "little pirate games", even refusing to take the Straw Hat Pirates and Heart Pirates seriously despite them crippling his SMILE trade; this is reinforced by his belief that defeating a Shichibukai is nothing to be impressed with and his dismissal of Donquixote Doflamingo as being weak.
Kaido is a very heavy drinker and, while drunk, his mood changes erratically, such as when he quickly went from being melancholic over his inability to increase the number of his Gifters and fulfill his dream of having a crew consisting of only Devil Fruit users to becoming angry and violent, beating his subordinates and cursing Luffy and Law.
Like other people, Kaido has a unique laughing style: "Worororo".
Kaido cares somewhat for his subordinates, as Scotch confirmed that Kaido would be angry if he were to be attacked. His subordinates seem to respect him, as Scotch refers to him as "Kaido-sama" while Sheepshead calls him as "His Majesty". However, Kaido acts callously toward his subordinates when in an angry mood, having once sent his subordinates flying out of his fortress with brute force while smashing wanted posters of his enemies. Prior to his supply of SMILEs being cut off, Kaido's dream was to have a crew composed entirely of Devil Fruit users, which he wanted to be the best crew the world had ever seen.
Jack is one of Kaido's three right-hand men, implying that the Yonko has great trust in him and his power. However, when learning about Jack's failure to rescue Doflamingo, Kaido appeared to care more about the loss of his SMILEs than the loss of his subordinate.