|“||True resolve means cutting open a bright path through the darkest of fields!||”|
—Giorno, encouraged by Mista's determination.
Giorno's childhood was filled with unhappiness and loneliness due to bullies and the abuse of his stepfather until he befriended an injured gangster he saved. As the man protected Giorno, he learned that he could trust people and since then, he has become a more confident person.
A defining characteristic of Giorno, and shared among his peers through him, is his resolve (覚悟 kakugo, can also be interpreted as "preparedness"); something that can be described as his ability to make important decisions without hesitation and seeing them through to the very end. An ambitious individual, he readily takes any occasion to achieve his final goal of becoming a "Gang-Star". Upon beginning to cooperate with Passione gangster Bruno Bucciarati, Giorno wastes no time in infiltrating the gang, and steadily works his way up the ranks. His assassination of Polpo was partially a way to get a promotion from Bruno. Later, Giorno also tried to personally approach the Boss of Passione, and planned to plant a bug on him in order to track him.
Being a very serious teenager, Giorno's mind doesn't stray off the path from his mission and the goals he's set for himself. However, Giorno has occasionally thought about more mundane subjects such as the delicious margherita pizza from Naples, right before being attacked by Notorious B.I.G.. Giorno tends to approach many things with a calm demeanor, and demonstrates immense composure even in the face of dangers he might not understand completely. However, he can still become anxious when things go south. He rarely allows his anger to get the best of him, but shows moments of tranquil fury against certain enemies. At his worst, Giorno becomes desperate for solutions to problems, though never displays any true panic.
Giorno seems to have inherited both of Jonathan Joestar and Dio Brando's traits, with the former's being present towards peers and allies, and the latter's towards enemies. He has a good heart and wants to help out anybody who has shown him kindness, but casually disregards law. He was a petty thief when he first encountered Koichi and bribed the airport security guards before stealing Koichi's luggage. Overall, he follows his own morality without compromise. Giorno values life greatly and always seeks to never leave someone to die, even putting himself in danger if another can stay unharmed. In the same vein, he seeks to put a stop to the drug trafficking which is ruining countless lives in Italy. On the other hand, Giorno has no trouble or qualms in punishing those that needlessly and intentionally hurt other people, as shown when he engineers Polpo's death to avenge a janitor that Black Sabbath killed, and in fact he will be particularly ruthless and vicious when doing so. Except for Bucciarati, whom he spared because he recognized that he was a moral person, Giorno has killed everyone he fought against without remorse or hesitation, and they all died a gruesome death. For instance, he had Melone bitten by a venomous snake and rapidly kicked Ghiaccio until a splintered lamppost had completely impaled his neck. In the presence of those same enemies, he is not even above lying, having deceived Cioccolata into believing that he would be spared, when in reality he was merely lowering Cioccolata's guard and buying time for a bullet to transform into a scarab which devoured the scientist's brain before Gold Experience pummeled him to death, sending his mangled corpse into a garbage truck as Giorno walked away unfazed.
Usually introverted, Giorno regularly maintains a facade of confident boldness, backed up by his intelligence and his natural charisma, to make him look like a flawless person by his peers. This is especially visible upon his first meeting with Bruno's team. He switches from a passive and polite demeanor to a self-assured persona when they try to bully him, and impresses the whole team. When alone, Giorno is shown to be a more goofy person and only in these moments does he allow himself to think about something else than his goal or act seriously. His parents' abuse encouraged his introverted nature and his habit of observing others, resulting in his deductive skills but also making him a silent person until he has something of importance to say. On the contrary, when Giorno has an enemy at his mercy, he is prone to chitchat, either lengthily exposing his way of life or analyzing their thoughts. Thus, he is much like his father Dio, and even taunted Diavolo during their climactic battle. Giorno is polite in his interactions with figures of authority or his superiors, and in fact doesn't swear at all. He nonetheless doesn't shy from expressing his opinions even if they contradict those of his interlocutor, as seen when he argues against Abbacchio about abandoning Fugo to the enemy.
Giorno also has the habit of assuming the responsibility of his actions alone, leading to a temporary state of panic when his plans fail. Giorno is very upset when he cannot do anything about his situation, going as far as to deeply apologize to Mista for being unable to use his Gold Experience against Ghiaccio's White Album. Over the course of Vento Aureo, he slowly learns to trust his teammates. Likewise, the rest of Bucciarati's gang are one-by-one charmed by Giorno's resolve and courage in them, with some like Mista and Narancia even thinking him more of a leader figure than Bucciarati himself. Instead of assuming control or acting by lonesome, Giorno eventually fully cooperates with them.
Making Giorno repeat himself greatly annoys him, as he believes it means his conversational partner is stupid. This is especially ironic, since his own battlecry consists of angrily repeating "Muda!". In addition, much like Jotaro, Giorno is annoyed by the numerous girls flirting with him and bluntly dismisses them.
- Dio Brando: While Giorno has never been shown interacting with his birth father, he has been shown to value his birth father to some degree as his wallet was revealed to contain a photograph of Dio. Giorno does inherit some of Dio's ruthless and brutal nature, as well as his ambition and charisma. However, he does not use it for evil ends. Giorno even uses the "WRYYY!" scream at one point.
- Jonathan Joestar: Unknown to even Giorno, his biological ancestry comes from Jonathan's DNA. As Dio conceived him using Jonathan's body, this allows Giorno to gain the Joestar Birthmark. From Jonathan, Giorno appears to have inherited his noble, polite, and overall kind nature toward good people, observed by Koichi to a degree. Even though Dio is the one whom conceived Giorno, and is believed by the boy to be his father, Jonathan is technically and by all means also the father.
- Mother (surname Shiobana): Giorno's mother had seldom cared for him when he was a child, viewing him as a hindrance to her party life and left him in the dark, where he was too scared to even cry.
- Stepfather (surname Giovanna): Initially, Giorno's stepfather would often beat Giorno when his mother was away. This changes after Giorno meets the gangster, after which the stepfather was likely intimidated out of trying to beat Giorno again.
- Donatello, Rikiel, and Ungalo: Giorno's half-brothers. It is unknown if he was aware of their existence.
|“||This Giorno Giovanna... it looks like he has a talent for getting people to accept him.||”|
—Bruno, Chapter 456
- Giorno's Hero: When he was little, Giorno saved a wounded gangster by lying to his pursuers about where he was. Incidentally, Gold Experience subconsciously intervened by making the grass and other flora around the gangster grow. The man was grateful and ensured that Giorno would never suffer in his life, making Giorno's stepfather stop beating him, and stopping anyone from bullying him. He taught Giorno that there was good in humanity, and although he objected to Giorno joining a gang, Giorno dreamed of becoming a "gang-star".
- Bruno Bucciarati: Giorno and Bruno met as enemies, but Giorno was able to deduce from the flaws in Bruno's tactics against him that Bruno was a good person, and decided to work with him in the conclusion of their fight. From that point on, the two have formed a relationship of mutual trust, even with Giorno unconditionally accepting that Bruno will not help him if he is found out as an enemy of Passione, while Bruno assists him in rising in the ranks. Giorno is able to save Bruno from complete and utter defeat at the hands of the Boss using one of his ladybug brooches, causing him to mentally note how Giorno always fills him with courage. After Bruno's soul is finally put to rest, Giorno immediately fights Diavolo, revealing his emotions towards his friend's death.
- Guido Mista: Mista is one of the initially nicer people to Giorno in the gang when he first joins and is quick to grow to him after seeing him in action. Mista is the second to realize Giorno's ability to guide others without their knowledge, viewing him as a source of hope. The two frequently team up together and have a lot of faith in each other's abilities, at one point combining their Stand powers in a moment of doubt to capture a helicopter. By the end of the story, Mista and Giorno are the surviving members of the original six-member team, and perhaps closer friends than the rest and continue to work together in the gang when Giorno takes over as boss with Mista as his subordinate.
- Narancia Ghirga: Narancia shows himself to be of higher stature to Giorno due to being older, though is easily stupefied by his talents. However, Narancia later trusts Giorno to fight with him against Squalo and Tizziano, even believing that the gang stood a chance against the boss if they had him. Giorno, after Narancia's sudden death, places a grave for him and vows revenge against his killer.
- Pannacotta Fugo: Fugo initially saw Giorno as an arrogant punk, like Abbacchio. During the struggle with La Squadra di Esecuzione member Illuso, he sees Giorno's worth as he sacrifices his hand, temporarily, to trick Illuso to be killed by Purple Haze, earning Fugo's respect, and making him the first next to Bucciarati.
- Leone Abbacchio: Abbacchio is highly suspicious toward Giorno's presence in the gang, even going as far as to deny Giorno the right to see his Stand in use while he tries to interrogate an enemy, during which time Giorno passively takes the abuse and tries to act in cooperation. During the battle with Illuso however, Abbacchio tries to sacrifice himself to allow Giorno to retrieve the key to the turtle shell and get it to the rest, and later shows a begrudging respect for him when he defies this and stays to save the lives of all the members involved in the battle. Never shown completely warming up to Giorno completely as the rest of the team has, Abbacchio nonetheless loses all suspicion toward him at the time of his death. It is Abbacchio's partner's ideals about always seeking and believing in truth that is shared by Giorno, allowing him to properly defy Diavolo's own beliefs during the final confrontation.
- Koichi Hirose: Koichi was sent by Jotaro to investigate Giorno. Despite the fact Giorno stole his luggage, they later became friends.
- Trish Una: The two don't interact as much, but Trish is seen to believe in Giorno's ability, and likewise Giorno sees potential in her as he leaves her with a new hand for him during the battle with Notorious B.I.G., a gambit which could have cost him the use of his Stand if she had failed to return it to him and Bucciarati. Her Stand, Spice Girl, openly admits that Giorno's actions have allowed her spirit to mature. Trish, like the rest of Bruno's team, has put her faith and trust in Giorno by the end.
- Jean Pierre Polnareff: Polnareff, after his body switch, becomes a guardian for the Stand Arrow and stays with Giorno and the newly-led Passione with the rest.
- Diavolo: As the Boss of Passione, which was selling drugs in the streets, Diavolo was de facto Giorno's archenemy and target. However, both didn't know or even personally meet each other until very late in Part 5. Knowing nothing about Diavolo, Giorno sought to approach him in order to take over Passione, but Bruno's open rebellion hasted his plan. While Diavolo learned very quickly how resourceful Giorno was and treaded carefully around him, he still treated him as inferior, calling him a "brat" and "hindrance". On the other hand, Giorno only got to interact with Diavolo when he acquired Gold Experience Requiem and used the one moment to challenge and taunt the boss.
- Polpo: Giorno met Polpo to pass the test to enter Passione. Giorno and Polpo were civil toward each other, but Polpo only saw Giorno as a potential tool and used his position of power to grimly warn the teenager about misconducting oneself. On the other hand, Giorno despised him as soon as his Black Sabbath killed a hapless civilian, prompting him to kill Polpo as soon as he could.
- Baby Face: Giorno and Baby Face were enemies, and the Stand Baby Face tried to assassinate Giorno to make a getaway after capturing Trish and Bruno. Baby Face grew increasingly frustrated at Giorno's determination to the point it forewent any precaution and tried to fight him openly. Ironically, Giorno thanked Baby Face for giving him enough trouble to be pushed into a wall and progress. It didn't prevent Giorno from summarily killing it and sending a venomous snake after its user, Melone.
- Cioccolata: While Cioccolata didn't think much of Giorno, only noticing that he discovered Green Day's ability rather quickly, Giorno witnessed the ruin Cioccolata's Stand brought to Rome, and execrated the psychopath. When Giorno defeated Cioccolata, he reminded the mad doctor that he didn't deserved to live and vented his scorn with a lengthy and mortal pummeling before throwing Cioccolata's mutilated body into a garbage truck.