The Carrie Diaries begins in Castlebury, Connecticut in 1984. Carrie Bradshaw comes back from summer break to her junior year of high school after recently losing her mother. She is welcomed back by her best friends Jill aka ‘Mouse’, Maggie and Walt. As Carrie returns to her old stomping grounds, she meets and has an attraction to Sebastian Kydd, a new senior and transfer student who was kicked out of his former school.
Carrie’s father, Tom, informs her that she can have an after-school, once-a-week internship at a law firm in New York City. Carrie sees this as an opportunity to start a new adventure and leave her small town behind. During her first day in New York, Carrie meets Larissa Loughlin, an editor at Interview magazine, and is fascinated by her life and career. She begins to juggle school, an internship, friends, boys and a blossoming enthusiasm for fashion. Larissa sees that Carrie has a unique bag she carries. Larissa asks Carrie to bring her bag to a photo-shoot to be featured in Interview magazine. Carrie is beside herself with excitement.
Back at school, Carrie gets closer with Sebastian and the two finally kiss in the pool. Carrie’s sister tells their dad about the romance and he tells Carrie that she should not be dating Sebastian. Carrie finds out that her dad represented Sebastian when he got kicked out of his old school. She snoops though her dad’s legal files, and discovers that Sebastian had an affair with one of his teachers. This causes Carrie to doubt her feelings. When Carrie informs Sebastian that she knows why he was kicked out of his former school, he decides that they should not see each other anymore.
Carrie runs into an old friend, named George Silver at her internship and gets invited to his mother’s dinner party in Manhattan, but her lingering feelings for Sebastian get in the way. That is until she sees him with another girl, who happens to be her arch-rival Donna. Elsewhere, Tom loses his wedding ring, which makes him realize that it might be right to start dating again.
On Thanksgiving, Carrie gets in way over her head when she tries to cook the perfect dinner for her family and her new boyfriend George and his father. Sebastian learns that his neglectful and divorced mother has decided to fly out of town with her much younger boyfriend, leaving him to fend for himself on Thanksgiving with nothing but a bottle of liquor.
Carrie continues to be torn between her new feelings for George and Sebastian, who is still dating Donna. When Larissa, unaware that Carrie is a 16-year-old, offers her a job working at Interview magazine, Carrie must make a tough. Later, Carrie accompanies George to her school’s dance where she tries to make Sebastian jealous by dancing and flirting with George.
When she receives an invitation by Larissa to a hip party in New York City, Carrie decides to take advantage of her school’s annual senior-junior shut-in to sneak out to the city and have some fun. After Sebastian stops seeing Donna, he seeks Mouse’s advice to help him get Carrie back. Tom takes the plunge and goes on a date in the city. Unfortunately for Carrie, she runs into her dad while out in the city and brings her secret world out into the open.
With Carrie forbidden from going to New York City ever again, she is told to look after Dorrit for the evening. When Dorrit goes missing, Carrie calls Sebastian for help, the one person who can help her find Dorrit before their father comes home.
As Carrie’s 17th birthday approaches, she is torn between spending the day with her friends, and a chance at losing her virginity to Sebastian, or an opportunity to mingle with New York’s literati at a party with Larissa.
Carrie decides to attend Larissa’s party but Sebastian decides to bail.
Later at the party, Sebastian crashes and gets drunk. Carrie is forced to drive him home in order to avoid causing a scene. Carrie sees the mansion where Sebastian lives and witnesses first-hand his unhappy home life, in particular his vain and selfish mother.
Word on the street is Carrie’s relationship with Sebastian has some rocky turns ahead.