Confessions of a Shopaholic stars Isla Fisher as Rebecca Bloomwood, a ditzy shopaholic who maxes out several credit cards while trying to keep up with the latest fashions. Dogged by credit collectors, she tries to get a job with Alette, a famous fashion magazine, but loses the job to a more sophisticated applicant. When one of the magazine's employees suggests that she might be able to work her way up to a position at Alette by working for one of the company's lesser known papers, Rebecca tries to bluff her way into a job writing for a financial magazine Successful Savings. By pure accident, she ends up getting the job.
Despite the fact that she has not handled her own finances well, she writes a column advising others on how to manage money. She uses the pen name "The Girl with the Green Scarf" and uses her experiences with clothing to teach financial lessons. Her column is widely successful, because rather than appealing to those who already have good business sense, it puts a more human element into the world of finances.
Yet not everything goes well for Rebecca. While employed at Successful Savings, Rebecca begins to fall in love with her boss Luke, played by Hugh Dancy. But she damages not only her relationship with Luke, but also her relationship with her best friend by continuing to act selfishly and shallowly.
Eventually, Rebecca re-evaluates her choices and begins selling all her beloved clothes. Through the sale, she makes back enough money to pay her debts. Her reformed attitude helps her win back her friendship and to patch things up with Luke.
Toward the end of the film, Rebecca is offered the job she coveted at Alette magazine, but, because her priorities have changed, she turns it down. Instead, she ends up working for Luke at his new company.
The film features appearances by Krysten Ritter, John Goodman, John Lithgow and Joan Cusak.