The following are the characters of the The Summer I Turned Pretty trilogy.

Main Characters

See: Isabel "Belly" Conklin 

Isabel Conklin - The main character and protagonist in the series. She is the daughter of Laurel and younger sister of Steven. She is known to be persevering, head-strong, sometimes domineering, and yet equally fragile. She looks for the best in everyone even when they fail to give it to her, even when they hurt her so deeply she can barely stand it. She is loyal and always striving for more. She has had a crush on Conrad since she was young but her relationship with him falls apart and the end of It's Not Summer Without You gets together with Jeremiah after he kisses her making his feelings known to her. In We'll Always Have Summer, which sees the two years the couple have been together, she discovers at a frat party that he cheated on her with a girl in his sister sorority on a vacation (who was known as the sorority "slut" by almost every girl in the sorority) which not only results in her literally slapping him (marking the first time she ever struck someone) but her spending days literally in bed crying. It is implied that her love for Conrad, despite being with his brother, in the following novel is just as alive as ever though and often finds herself torn between the two brothers.

See: Conrad Fisher 

Conrad Fisher - The eldest son of Susannah and Mr. Fisher and older brother of Jeremiah. He is known to push away his loved ones aside as is known to keep all his emotions and feelings inside and rarely, if not ever, expresses them. He’s rebellious, stubborn, and infuriating a great deal of the time. In the first book, his character is something of a jerk or "asshole" to everyone having spent the summer getting drunk and locked in his room. It is suspected though, however, that he has developed feelings for Belly; having shown several accounts of getting either overly protective or jealous of guys flirting with her. At the end of the novel he gets together with her. However, the relationship is short lived when Conrad once again slips back into his "asshat" ways and pushes her away and their relationship ends on a sour note as seen in flashbacks in It's Not Summer without You. Though by the last installment of the series, he is still in love with Belly and ends up confessing his love for her when unable to repress his feelings any longer. 

See: Jeremiah Fisher

Jeremiah "Jere" Fisher - The supposed golden boy. At the outset of the series he is the good boy, the one that appears to be golden in the eyes of everyone. The stabilizing and supportive force in the family where Conrad is known to be the turmoil. He is a good friend to Belly and a loving brother to Conrad and even steps aside as Conrad pursues Belly when he wants her for himself. Although by It's Not Summer Without You, he is tired of burying his feelings for Belly and abruptly kisses her while sitting in a car with her, who in return, kisses him back. However when things begin to get heated, they are walked in on by Conrad, who in reaction, is near furious. Despite this however, Conrad gives Jeremiah permission to have his chance with Belly. By the third book, his character goes through an ugly transformation from Golden Boy to Frat Boy and even cheats on Belly with the "sister sorority slut" and proposes to Belly to prove his guilt, but however is shown to have dramatically changed for the worst.

Susannah "Beck" Fisher - The rock that everyone seems to cling to. She is sick of cancer throughout the first novel, which kills her by the beginning of the second follow up book. Despite this, she is heavily remembered by her family and friends throughout the remainder of the series. It is discovered she left letters to all of her "summer kids" in the final book (although we only get to read the one she wrote to Belly). She is shown to be very friendly, loving and compassionate. Her death hits everyone hard and life without her seemed near impossible and takes everyone almost a year to pull themselves together and to form a life without her existence.

Regular Characters

Adam Fisher - A man who is known to have his way no matter what it costs or who it hurts. He is Susannah's husband and father of Conrad and Jeremiah. After she dies he turns to whiskey. He drove Conrad away after Conrad saw how badly he began treating Susannah, such as cheating on her and running away when she got cancer. He tries to sell the summer house in It's Not Summer Without You after she dies and barely stopped in time by Laurel and Conrad and everyone else (excluding Steven who is away in college.)In the final book, he tries to mend his relationships with his sons and pays for Jeremiah and Belly's wedding despite not agreeing with them on getting married at such a young age.

Taylor Jewel - Belly's best friend despite being her polar opposite. She is boy crazy and shallow, though she grows up and sheds her childish personality. In the first book of the series as seen in flashbacks, she is boy crazy and considered something of a slut as she goes for all three of the guys (Steven, Conrad and Jeremiah) almost at once (first setting her eyes on Conrad and flirting with him, then kissing and leading Jeremiah on and then getting caught kissing Steven in less than a week) despite telling Belly that girls "can't do that." She is seen desperately trying to pair Belly with guys and trying to get to "show some cleave" despite Belly's endless protests of doing such things. She and Belly gradually begin to drift apart by We'll Always Have Summer while moving on in their lives, but still remain close friends. This can be seen as Taylor supports Belly in her decision to have a wedding. She confronts Conrad, after suspecting he said something to Belly after noticing a change in her behavior, and warns him to leave her best friend alone as he has only hurt her endlessly in the past. Despite this, she says Belly told her a part of her will always love him and reveals that she knows he loves Belly too and that "only he can stop her from marrying Jeremiah" but to be "damn sure he still wants her [Belly]", However, she urges him to "be the good guy Bell says he is" and to "let her go." 

Laurel Conklin - Belly and Steven's mother as well as Susannah's best friend. She is rigid and desperate to have the relationship with Belly that her daughter had with her best friend Susannah. She seems to always make the wrong choices as far as Belly is concerned but her desire to be close to her daughter is prevalent and admirable. The two young women come head to head in We'll Always Have Summer when Belly and Jeremiah announce their engagement and Laurel is furious saying the couple are far too young for such a commitment, even going as far as refusing to show up for the wedding and even kicking Belly out of the house. Conrad though, talks to her and manages to convince her to make amends with Belly. It is shown in the final book that the relationship between Conrad and Laurel is very close and even resembles the relationship between Conrad and Susannah. In the epilogue of We'll Always Have Summer it is implied that she helps Belly pick out her wedding dress for her and Conrad's wedding and helped plan it (just as Belly always dreamed and hoped of having her wedding).

Other Characters

Steven Conklin - Belly’s brother Steven is a good friend and supportive brother. Though we see little of him overall his truthfulness is a springboard for Belly to make difficult but wise decisions. He appears throughout Belly's flashbacks making fun of her and teasing her endlessly but despite such teasing is shown to have a protective side of her. This in which is also supported from a statement from Jeremiah from one of the chapters of It's Not Summer Without You who states that Steven despite his constant teasing was "really protective of Belly." Even saying to Belly herself in We'll Always Have Summer that while Jeremiah was like a brother to him Belly was his "little sister and [she] came first." Something that even surprises Belly herself. 

Cam Cameron - Belly's first boyfriend and the first guy who ever called her beautiful. He only appears in the first novel of the series being a summer fling for Belly. It is told he had a crush on Belly throughout grade school but never had the courage to approach her. He left one final voice message for Belly asking if she wanted to stay in contact after the summer but if not "it was nice hanging out with her". He is mentioned twice more throughout the series afterwards as a summer memory for Belly.