Flighty, abrupt, and snappy with her elders, Jolyne in her teenage years was easily considered a delinquent and lost cause. Bitter at Jotaro for neglecting her, she tried multiple times to catch her father's attention by committing multiple minor crimes and went to jail several times for them. Because of Jotaro's neglect of his child, Jolyne was said to be dependent on the affection and approval of those around her, and she was ready to cover Romeo's accident, even if she was sentenced to 15 years in prison for it. As explained in Eyes of Heaven, she was fixated on spending time with her absentee father, and prolonged neglect was what made her start to resent him.
After acquiring her Stand and being told by Jotaro of his love for her, Jolyne noticeably matures, becoming more courageous and confident. "Reviving" Jotaro, who fell into a coma due to Whitesnake stealing his Stand and memory, turns into her first priority.
Jolyne retains her confrontational attitude throughout the story. A former delinquent living in a maximum security prison, Jolyne had to toughen up and can be especially rude. Her rare interactions with villains are either surly taunts or death threats, knowing how despicable most of them are. She also advocates aggressively asserting herself, especially in the prison, and once told F.F. to violently confront an inmate who cut in the queue for buying their lunch. Jolyne is particularly violent in her fights; she's used the cutting ability of her string to gruesomely wound her opponents, cutting off ears and nails for instance. Jolyne also has a vindictive side and repays tenfold any wrong committed against her, notably indirectly cutting Romeo's tongue for betraying her, moreover, Jolyne still holds a little grudge against Gwess, her first enemy and wants nothing to do with her despite the latter's effort to behave in front of Jolyne.
Jolyne possesses a fierce determination, carrying her through several battles and inspiring her companions. After learning of Dio's plan, Jolyne took pride in her lineage and opted to continue Jotaro's effort to seal the menace Dio left behind him. Jolyne stoically endures the hardships she faces and carry on her goal, disregarding the suffering and possible risks. Her determination is so great that she was willing to lose a limb or even her life to defeat her enemy and save her comrades, an inclination especially prevalent in her that culminated in her sacrifice to get Emporio away from Pucci. Even still, Jolyne once expressed her doubts about being able to stop Pucci after Weather Report's death and the priest's second escape.
Common in her lineage, Jolyne has honorable morals and treasures her family and friends. She would selflessly do everything in her power to help her companions and random victimized people, once helping a fellow mistreated prisoner to take back stolen money from her tormentors. Jolyne is willing to believe in the good in people, which resulted in a share of betrayals, but also earned her F.F.'s friendship. Jolyne is especially sweet to Emporio, her real first ally in Green Dolphin Street, and despite being an enemy, Jolyne didn't want to kill the Green Baby. Jolyne's primary motivation for investigating Whitesnake was her love for her father, and Pucci exploited that affection to escape her the first time.
Outside of combat, Jolyne behaves like an average teenage girl, hanging out with her friends and occupying herself the best she can in the prison, as she is also fun-loving. Jolyne notably played ball with F.F. and Ermes, and made herself a navel ring while in isolation. Unlike her father, Jolyne is rather extrovert and easily expresses her feelings to others. She is a sociable woman, and can converse with her fellow prisoners easily, asking for explanation about the ins and outs of Green Dolphin Street.
Jolyne is notable for being somewhat libertine, being the first and only JoJo to admit to masturbating, and offhandedly commenting that snails' ability to copulate with anything makes her slightly jealous. Jolyne also mention her need to urinate in the middle of a fight with another person, a man at that. She is horribly embarrassed to talk about it in public and being caught in the act by a guard flustered her deeply.
Araki created Jolyne with the hopes of "making up" for his previous (and in his eyes, failed) attempt at a female protagonist. Aside from offering an interesting contrast to most shonen comics, he thinks she is a "real woman" sorely lacking in the medium. The role reversal between her and her father was devised for her character to go beyond the typical archetypes found in Japanese fiction.
- Jotaro Kujo: Her distant and near-fatherless childhood bore a tinge of loneliness in her, at times resenting him but also wanting his affection. Her relationship with Jotaro is challenging at first, not really fitting the typical father-daughter mold. When Jolyne was fourteen, she was wrongfully accused of pickpocketing. Panicked, she stole a car, sloppily tried to make an escape from the authorities, and was arrested soon afterward. Jolyne anticipated that Jotaro would pay her bail, but was sorely disappointed when she overheard her mother's frantic and unsuccessful pleas with him on the phone. Her father's absence following this led to her teenage years of delinquency (she later reflects that these events were a desperate call for attention). During Jolyne's imprisonment, Jotaro visited her in an effort to break her out. Angered that he would come out of the blue to see her after years of neglect, Jolyne blew up at him, citing his inattentive behavior and his divorce. However, after risking life and limb to get Jolyne out as well as losing his Stand in the process Jolyne broke down and got Jotaro to safety, sacrificing her own freedom and vowing to get his Stand back. As time passed, Jolyne came to respect her father more and idolized him somewhat, adapting his trademark "Yare yare daze" into a more feminine "Yare yare dawa". When Jotaro returns later, both father and daughter show considerable care to one another, each in their own way.
- Mother: Jolyne's mother rarely appears and is hardly talked about. It's assumed that she loves Jolyne very much and dotes on her in Jotaro's absence, as she was the only known person to be allowed to call Jolyne "JoJo". It's mentioned that she is an Italian-American, making Jolyne 1/4 Japanese, 5/8 Italian, and 1/8 British.
- Holy Kujo: It is unknown if Jolyne has a relationship with her grandmother. However, she is shown at times to demonstrate the kindness Holy often did.
- Ermes Costello: Ermes is possibly the first true friend that Jolyne encounters in her life due to the two being held up in the same holding cell in the very beginning. Her relationship with Ermes is possibly the closest she had beside her mother, resembling Jotaro's relationship with Jean Pierre Polnareff. She has fought alongside Jolyne against many powerful enemies like Sports Max, Rikiel, & Donatello Versus.
- Emporio Alnino: Emporio's relationship with Jolyne is somewhat similar to her great-great-great grandfather Jonathan Joestar to Part I's Poco, due to how she saves him from many dangerous situations & even giving her life so than he may live. Emporio's relationship with Jolyne extends to SBR's Irene as well.
- Foo Fighters: Foo Fighters initially met Jolyne as enemies however, after that they became quick friends. Foo Fighters, nicknamed F.F. , is shown as the more comical of the trio, as "she" has a more light-hearted disposition to life in the Green Dolphin Street Prison. The two have aided each others lives many times, as F.F. healed Jolyne after her many battles.
- Romeo Jisso: Jolyne's former boyfriend is depicted as a cowardly rich kid. She gave him permission to call her Jojo (if she could call him Rome-chu). Their relationship ended when Jolyne discovered that Romeo had framed her for a murder, landing her in prison for a crime she didn't commit. After she escapes from prison, Jolyne pays him a visit and he weeps for forgiveness. She hushes him, asks for cash and a car, and, after warning him not to betray her again, leaves him. Ermes held a duplicate of his tongue which transmitted whatever he said aloud and also served as a quick silencer should he chose to report them. Romeo gets a call from the police moments later but he misleads them, saying that Jolyne was headed for Mexico (when she's actually hunting Pucci). Though touched by his surprising loyalty, Jolyne still removes the sticker to rip his tongue apart.
- Weather Report: When they first met, Jolyne seemed somewhat speechless around him (rare for her usually energetic personality). Anasui even suspects him to be a rival for Jolyne's love and is jealous when Jolyne is with him. For a while, fans in Japan speculated that these two were the official couple for series 6 until his past revealed him to be well into his thirties. Regardless, there are hints of Jolyne caring for Weather in a more-than-fraternal way.
- Narciso Anasui: Though Anasui fell in love with Jolyne at first sight, the feeling wasn't mutual; Jolyne was not really sure what to think of him. He would sometimes try to seduce her in underhanded ways, such as asking F.F. to trip her down the stairs so he could romantically catch her or prompting a french kiss from a temporary-mute Jolyne. His romantic ploys are sources of comic relief, earning him a punch or tears of melodrama when he fails. Even so, he's truly devoted to her and will do everything in his power to keep her from being distressed. He has risked his life for her on more than one occasion and turns murderous when Jolyne is severely hurt. He's probably the closest to marrying Jolyne, as is hinted at the end of series 6 when Jolyne's alternate universe counterpart (Irene) states that Anasui's alternate universe counterpart (Annakiss) was going to drive them to meet with her father so that they could get married (In the first universe although he asked her father to marry her he didn't get a answer).
- Enrico Pucci: To Pucci, he only saw her as bait at first in order to get to Jotaro but proved to be a bigger threat upon her determination on getting her father's Stand and memory disks. They became enemies right away once informed that Whitesnake was in fact Pucci and was eager to take his life but Pucci proved himself to be a lot more challenging when he threw her father's memories into a dying Anasui which gave Pucci the edge of achieving victory. Jolyne became more then determined in stopping him and putting an end to his plans but her efforts would soon be fatal while she almost fell to Pucci's newly evolved C-Moon and would finally fall to his Made In Heaven while protecting Emporio, but has managed to cut the right side of his eye before dying.
- Donatello Versus: Due to his alliance with Pucci, Donatello and Jolyne were enemies. An additional reason for their antagonism would be that Jolyne's father destroyed Donatello's father. In the end Jolyne accidentally killed Donatello after being tricked by Whitesnake into thinking he was Pucci. Unbeknownst to either of them since Donatello was conceived when Dio possessed Jonathan's body Donatello is actually Jolyne's distant uncle.
- Johngalli A: As the man who got her framed for murder, Jolyne greatly hated Johngalli. Johngalli attempted to murder Jolyne to avenge Dio but failed. Jolyne would fail to get her revenge as he would be killed by Pucci after their fight.
- Gwess: Jolyne's cellmate during her time at Green Dolphin. Jolyne inadvertanly awakened Gwess's Stand power with her amulet, which was created from arrow fragments. Gwess originally used her powers to bully Jolyne, but after Jolyne beat her she acted like her subbordinate.