Cammie is a 15-year-old sophomore at the Gallagher Academy for Exceptional Young Women, a covert training facility for spies. Operating under the code name Chameleon, she excels at blending into crowds and remaining unnoticed. While her invisibility makes her a highly capable operative, it also leaves her feeling personally insignificant. She longs for an ordinary teenage experience, prompting her to maintain a double life when she meets a boy from town.

A newcomer to the academy and the daughter of a prominent senator. Macey initially presents a disrespectful attitude, having been expelled from several traditional schools. Her extensive knowledge of the outside world, fashion, and teenage boys makes her unexpectedly valuable to Cammie's attempts to blend into normal society.

An average teenage boy from town whose parents own the local pharmacy. Josh feels constrained by the expectation that he will eventually inherit his family's business and longs for a broader worldview. Unaware of the Gallagher Academy's true nature, he views Cammie simply as a homeschooled girl, providing her an escape from spy training.

The new Covert Operations professor at the Gallagher Academy. A rugged operative with extensive field experience, he immediately becomes a heartthrob among the students. His teaching style is demanding and practical, pushing the girls to confront their weaknesses and observe their surroundings critically.

Liz is one of Cammie's best friends and roommates at the academy. She represents the intellectual side of espionage. Possessing genius-level intelligence, she excels in logistics, science, and computer hacking rather than physical combat. She is highly dedicated to her friends and frequently monitors communications to ensure their safety.

Cammie's roommate and best friend operates as the group's muscle. Bex is confident, athletic, and possesses a confident swagger. As the only non-American student at the academy, she excels at physical stunts and combat, fitting the traditional action-oriented profile of a spy.

Cammie's mother and the headmistress of the Gallagher Academy. She balances the massive responsibility of running an elite, top-secret training facility with her role as a single mother. She makes controversial administrative decisions but remains deeply protective of the students.

A local teenager who attends school with Josh. Dillon harbors a strong prejudice against the academy, fully believing its cover story as a facility for spoiled, wealthy girls. He acts as a bully whenever he encounters the academy students in town.

The historical founder of the Gallagher Academy. A legendary spy known for stopping an unknown assassin from targeting Abraham Lincoln, she represents the legacy of female espionage that guides the school's current mission.