There are numerous discrepancies in the various media depicting Carmen Sandiego and there are no official rules establishing a correct canon. However, the following seems to have remained consistent throughout all Carmen Sandiego media created since around the mid-1990s:
- In most Carmen Sandiego media, it is stated or implied that the title thief steals only for the challenge of it, although some of her V.I.L.E. minions seem to be more traditionally motivated. She often describes her schemes and the user/protagonists attempts to stop them as being a game, which they ironically are, regularly gloating that she is impossible to capture or that her plans are infallible and acting as though any efforts made against her are extremely trivial. Sometimes, she asserts that it is impossible for anyone to understand her or her motives and seems to revel at how difficult she can make it for anyone trying to figure her out.
- In the original Where in the World Is Carmen Sandiego? game from 1985, it is stated that Carmen is a former spy for the Intelligence Service of Monaco and that she is "an agent, double agent, triple agent, and quadruple agent for so many countries that even she has forgotten which one she is working for," but this background seems to have since been abandoned. Carmen now has a different origin story which has been consistently maintained for over a decade. Typically, it is explained that she was an ace detective for the ACME Detective Agency who found catching criminals too easy and decided that outsmarting ACME itself would make for greater challenges.
- In both the animated TV series Where on Earth Is Carmen Sandiego? and in the video game Where in the World Is Carmen Sandiego? Treasures of Knowledge, it is heavily hinted that, despite her thieving ways, she may still have some goodness left in her. The character has, however, never been depicted turning back to the "good" side outright, although she has often been encouraged to do so. Nevertheless, Carmen tries to maintain a reputation as a "thief with a conscience" in the Earth series and ACME agents who used to work closely with her are often shown to have mixed feelings about imprisoning her.
When the computer games first debuted, Carmen was not given much of a character outside of mentioned hobbies and preferred activities (other than theft of geographical landmarks). During the time of the game shows, she was given a slightly better insight in terms of character, but still not given much of a personality other than being an "evil for evil's sake" villain.
The most personality that Carmen has shown in any of her media was in the "Where on Earth" cartoon series. With the more profound analysis of her backstory, her character was expanded and more-so changed into that of an anti-heroine, having become a thief not only because it was her ideal of a better life with more "fun", but also for the mental challenges and thrills the lifestyle provided. While she does still command V.I.L.E., she is mostly seen working by herself in a major heist, while her henchmen provide support in the background or simply make the way clear for entry.
Despite her major power over V.I.L.E., Carmen follows rules of her own regarding her crimes, the most important being that she doesn't kill or harm her rival ACME agents, with a special care taken towards siblings Zack and Ivy, her most active pursuers. She will actively aid them if something goes wrong during a chase and their lives are on the line because of it, or if a villain with the same power as hers tries to attack them outright. She will also never carry on with a heist if it involves putting someone else in danger (unless Lee Jordan blackmails her into it), and while she doesn't show regret over putting someone in danger, said "danger" is often something that never truly harms the chaser, partially justifying her lack of worry.
Carmen has been also shown to be extremely hard to defeat in an emotional level, and rarely ever cracks under pressure, even though it can indeed happen. While she treats every new heist as a game, there are times when the case becomes personal enough to make it serious for her and anyone else involved, and while not a traditional and superstitious person, Carmen does not believe in exaggerated coincidences, or acts disrespectfully towards other cultures, and might even use one of her crimes to solve personal problems involving these cases.