Age: 13-15; 23-25
Date of birth: September 9
Height: 168.5 cm
Nationality: Japanese/Italian
Known relatives: Bianchi (Half-Sister), mother (deceased), father
School: Namimori Junior High
Grade: 1st year, 2nd year (later in the series)
Rings: Vongola Ring of Storm, 4 Rings from Sistema C.A.I.
Box Weapon: Leopardo di Tempesta ver. Vongola (Uri)

Gokudera was born in Italy and is 3/4 Italian and 1/4 (mother) Japanese. His blood type is B, is 168 cm tall, weighs 54kg and his hair is silver. His future dream is to become the Tsuna's right-hand man. He has an ability to play the piano. He dislikes people that are older than him, Bianchi and Lambo. Gokudera is also a chain smoker, but they remove this in the anime adaptation.

At school, Hayato is adored by many of the female classmates who view him as the "rebellious badboy." During Valentine's Day, a large group of females constantly followed him around trying to give him chocolate, although Hayato seemed to be more annoyed than flattered by this. Despite his image of a rebel, Hayato excels in his schoolwork and aces all his tests, much to the surprise of Tsuna. This is probably due to his rich upbringing, suggesting that he probably had a multitude of private tutors when he was young. He idolizes Tsuna greatly and considers himself to be Tsuna's right-hand man.

Due to a traumatic childhood experience, every time he sees the face of his older sister, Bianchi, he becomes sick, sometimes even falling unconscious. Oddly enough, he is immune to his sister when she happens to be wearing something that covers part of her face (i.e. glasses or goggles).

When he was younger, he was a talented pianist. However, he soon grew tired of playing after his 'trauma', and instead, decided to join the Mafia. Unfortunately, since he was considered to be a mere pianist, no one wanted to accept him into their family; the fact that he was an oriental half-breed lessened his chances of finding a willing Mafia family to take him in. To become stronger, he sought advice from Dr. Shamal, who, at the time, was working for his family. Hayato seemed to have looked up to Shamal, to the point that Shamal believed Hayato to have copied his hairstyle, and even wanted to learn his assassination technique, the Trident Mosquito. Instead, Shamal taught him how to use dynamites, which caused Hayato's fascination with explosives, eventually choosing them as his main weapons.

In the future arc, more was revealed of Gokudera's past. He and Bianchi are actually half siblings, born by different mothers. Bianchi's mother was married to their father but Gokudera's was a woman with whom he had an affair. Gokudera's mother was a young, beautiful woman and a very talented pianist, whom their father fell in love with at first sight. Not long after, they became involved and the woman bore a child. However, in the mafia, illegitimate children are not tolerated, and everyone was told that Gokudera Hayato was actually from the same mother as Bianchi.

His real mother was allowed to see him three times a year until he was three, when she was killed after driving off a cliff on her way to see her son. It was probably not an accident, because, as Reborn says, "It slid off the road at an impossible location. It's been said that there weren't even tire marks. It was instant death." Suicide was considered, but she had been looking forward to that day and had even brought a present for the young Gokudera. Gokudera himself was unaware of what had happened until he was eight. He had overheard some servants gossiping and fled the mansion the day following.