Mia is a 14-year-old high school freshman living in a Manhattan loft with her artist mother. Deeply insecure about her tall frame and flat chest, she prefers to fly under the radar at Albert Einstein High School. Her carefully managed teenage existence changes radically when she discovers she is the sole heir to the European principality of Genovia.

Lilly is Mia's highly opinionated best friend and a fellow freshman at Albert Einstein High School. She hosts her own public access television show and thrives on launching social boycotts. Strongly opposed to monarchies, her blunt nature often causes tension when she tries to dictate how others should behave.

Helen is an unconventional New York City artist and Mia's mother. She rejects traditional societal expectations, leaving Mia to manage household responsibilities like paying bills and tracking groceries. Despite her disorganized lifestyle, she is fiercely protective of her daughter.

Phillipe is the Crown Prince of Genovia and Mia's father. A recent battle with testicular cancer leaves him sterile, forcing him to reveal his royal identity to his daughter so she can assume her place as his heir. He relies heavily on strict discipline and monetary bribery when dealing with Mia.

Grandmère is the Dowager Princess of Genovia and Phillipe's mother. Highly critical and prone to smoking in bed, she travels to Manhattan specifically to give Mia intensive princess lessons. She expects absolute obedience and takes aggressive steps to mold her granddaughter into a socially acceptable heir.

Lana is a popular cheerleader who continuously targets Mia with cruel remarks. As a quintessential high school bully, she leverages her popularity and relationship with Josh Richter to intimidate students she views as social inferiors.

Michael is Lilly's older brother and a student in Mia's Gifted and Talented class. He produces his own web magazine and frequently teases Mia, though his jokes hide a more genuine interest in her well-being. He notices Mia's strengths when others do not and steps in to tutor her in algebra.

Mr. Gianini is the algebra teacher at Albert Einstein High School. His decision to date Mia's mother creates immense awkwardness for Mia, especially since she is actively failing his class. He tries to be supportive of both Helen and Mia while maintaining his professional duties.

Josh is a handsome, popular senior on the crew team at Albert Einstein High School. He serves as the primary subject of Mia's daydreams, though he rarely notices her existence until her royal status becomes public. He prioritizes his social standing above all else.

Tina is a wealthy student at Albert Einstein High School who is ostracized by her peers because her overprotective father forces her to attend school with a bodyguard. She loves romance novels and quickly proves to be a loyal, supportive presence when Mia needs an escape from the popular crowd.

Lars is Prince Phillipe's personal bodyguard. He protects the Genovian royal family, which soon includes tailing Mia around Manhattan to ensure her safety once the paparazzi discover her identity.

Paolo is a high-end stylist hired by Grandmère to fix Mia's appearance. He completely transforms Mia's hair and applies fake nails, ignoring her personal preferences in favor of creating a more traditionally glamorous look.

Principal Gupta is the head administrator at Albert Einstein High School. She usually views Mia as a good, rule-abiding student and is highly surprised when Mia acts out in the cafeteria.

Boris is a Russian violinist who tucks his sweater into his pants. Lilly harbors a massive crush on him due to his musical genius, while Mia finds his fashion choices slightly confusing.