Employees at the Portland State University bookstore noticed one student was returning a lot of textbooks.
They found she had made 21 returns in March and April worth more than $2,000.
KOIN reports video showed her taking books from the shelf, putting them in her bag and "returning" them for cash.
The store manager called police and she was arrested Wednesday on theft charges.
The 26-year-old told police she needed money to pay off credit card debt.