Chloe O'Brian is exceptionally intelligent; in particular she displays extraordinary mastery of computer science. Spending most of her time behind a computer terminal, she is rarely sent on field assignments. She works very well under pressure, yet it is obvious when she is under pressure, and she has always demonstrated a degree of social awkwardness. She also has a complicated friendship with CTU Agent Jack Bauer.

In the beginning, Jack thought of Chloe as an annoyance, though that didn't keep him from using Chloe to engage in unauthorized use of CTU computer resources without their superior's permission. The relationship was one-sided initially, in terms of Jack using Chloe and demanding that Chloe risk her career on her blind faith that Jack was right. Chloe would reluctantly follow Jack's demands and ride out the problems they would make for her with her boss until Jack's requests from her yielded the results that he promised they would.