The characters from all books from the series are as follows:
Primary characters
- Persephone Mira Hadley: the co-protagonist of Noughts & Crosses, Knife Edge, & Checkmate, and a supporting character in Double Cross, Crossfire and Endgame. Nicknamed Sephy, the daughter of a powerful Cross, Kamal Hadley. She was childhood best friends with Callum despite their different backgrounds, and she eventually falls in love with him. After a few years pass without contact, Callum kidnaps her, but they end up sleeping together and have a daughter, Callie Rose, who is raised by Sephy and Meggie after Callum is killed. She later suffocates and falls out with Callie Rose after lying to her about Callum. She marries Nathan Ealing and has a second child, Troy.
- Callum McGregor: the co-protagonist of Noughts & Crosses. A Nought who is best friends and later lovers with Sephy. He is one of the few Noughts to get into Sephy's elite school, proving his intelligence, but he suffers discriminatory bullying from the other students. After losing contact with Sephy, he works for the LM and helps them kidnap her. However, his feelings for her return and he ends up sleeping with her, eventually helping her escape. He is hung for his involvement in Sephy's kidnapping before his daughter Callie Rose is born.
- Jude McGregor: the co-protagonist of Knife Edge, the main antagonist of Checkmate and a secondary antagonist in Noughts & Crosses. Callum's older brother; he holds a grudge against Sephy as he believes her to be responsible for his brother's death. He hates all Crosses but becomes romantically inclined towards a Cross, Cara. The resulting emotional conflict becomes too much and he beats her to death. He later attempts to use Callie Rose to get back at Sephy, training her to become a terrorist, but his plan backfires when Jasmine takes the bomb and activates it in his hotel room. Before he is killed in the bomb blast, he finally admits his feelings for Cara to himself, as she is the last thing he sees before he is killed.
- Meggie McGregor: Supporting character in all books. Callum's mother, who had been Sephy's nanny until Jasmine fired her. She convinces Sephy to move in with her and is very close to Callie Rose. However, a threat to call social services about Callie Rose estranges Sephy from her.
- Callie Rose McGregor: the protagonist of Checkmate and a supporting character in Knife Edge and Double Cross. The daughter of Callum and Sephy. She resents her mother for keeping her father's identity a secret, and joins the LM after being manipulated by her uncle, Jude. She intends to blow herself and Kamal up, but her grandmother Jasmine steals the bomb and locks her in the cellar with Sephy in a successful plan for them to make up. She enters a relationship with Tobey, her Nought friend, mirroring the unlikely relationship between her parents. Both she and Tobey go on to study law at university, but fall out.
- Tobias Sebastian Durbridge: The protagonist of Double Cross, and a supporting character in Checkmate, Crossfire, and Endgame. Nicknamed Tobey, he is Callie Rose's friend and eventual lover. He becomes involved with a dangerous gang but leaves the criminal life behind after Callie Rose is shot by one of the members, putting her in a coma. He manages to kill the leader, Alex McAuley, bringing the whole gang down in retaliation. Tobey and Callie Rose become a couple and both go on to study law at university. He eventually becomes Prime Minister, with the help of his friend, Daniel Jeavons.
- Troy Ealing: Co-Protagonist of Crossfire and Endgame. Sephy and Nathan Ealing's child; Callie Rose's younger brother. Nathan dies when he is young and is raised by Sephy alone. He dislikes Sonny because he believes Sonny killed his dad. Is kidnapped by Libby's mother, Misty Jackman along with Libby.
- Liberty Jackman: Co-Protagonist of Crossfire and Endgame. Nicknamed Libby, she's Tobey's and Misty's child. She is distanced from her father and is raised by Misty alone. Misty lives on the money Tobey gave to Libby, and Libby is furious when she realises this. On a student election day, Libby is kidnapped with Troy by her mother, Misty, who is later killed by Daniel's enforcers.
Secondary characters
- Jasmine Dharma Ninah Adyebe-Hadley: Sephy and Minerva's mother, who became an alcoholic. She used to be good friends with Ryan and Meggie McGregor, as Meggie used to work for her. She is diagnosed with breast cancer and, drinking less than before, steals and activates Jude's bomb, killing her and Jude in the process to protect Sephy and Callie Rose.
- Kamal Hadley: the main antagonist of Noughts & Crosses and a secondary antagonist in Knife Edge. A powerful, avaricious Cross Home Office Minister who will do anything to gain more power and influence. He is the father of Sephy and Minerva and the grandfather of Callie Rose, but disowns Sephy and Callie Rose. He divorces Jasmine after an unhappy marriage and remarries. A letter sent by Jasmine sent to the media ends his stint in power.
- Minerva "Minnie" Hadley: Sephy's older sister; she and Sephy are not very close, as Minnie is often shown to be quite selfish. She marries an affluent Cross, Zuri, and they have a son, Taj.
- Lynette McGregor: Callum's older sister, who is mentally damaged after being attacked by a group of Noughts for dating a Cross. Losing touch with reality, she fully believes she's a Cross. She eventually commits suicide by stepping out in front of a bus, but only Callum knows that it was not an accident.
- Ryan McGregor: Callum, Jude, and Lynette's father, who is killed trying to escape from prison after the Dundale bombing.
- Rebecca Dowd: Vanessa Dowd's daughter. She is a rich Cross who makes her money from drugs, illegal shipments and more. She briefly dates Tobey after falling in love with him but is killed by Alex McAuley, the Dowd family's archenemy. She is very lonely and Tobey loves her, unlike other boys, for reasons other than her family and her money. However, Tobey remains in love with Callie Rose.
- Daniel "Dan" Jeavons: Tobey's friend, who uses Tobey's desperate financial situation to introduce him to gang life. Dan later becomes a mobster and serves time in prison. He comes out and helps Tobey become Prime Minister with dirty tactics. Dan is killed by his butler for impregnating his daughter.
- Cara Imega: A kind-hearted Cross who falls in love with Jude. She campaigns against discrimination towards Noughts. Although Jude wants to take her money, he eventually falls in love with her as well. He becomes so confused about his feelings that he follows through with his original plan. He beats her to death and steals all her money.
- Sonny Devlin: A member of Sephy's band. Starts to go out with Sephy, but Sephy decides to end their relationship even though they have feelings for each other. He later murders Nathan due to jealousy.
- Nathan Ealing: The owner of a restaurant at which Sephy sings. They realise that they have feelings for each other and get married, having a son named Troy.
- Eva Foxton: An old nurse who becomes a mother figure for Dan, eventually succeeding him as the leader of his gang, the Outfit.
- Owen Dowd: Crime boss and associate of Dan. Brother of Rebecca. Murdered by Eva.
- Alex Mcauley: Main antagonist of Double Cross, a crime boss in a war with the Dowds. He tries to make Tobey join him, but is killed by Dan, who replaces him.
- Jarvis Burton: Dan's second-in-command, who, after his death, wages civil war on Eva, before replacing her as leader of the Outfit.
