"Little Black Dress" depicts the friendships, jealousies, hopes and failures of four 24-year-old girls. The girls first met as first year students in college. They seem to be enjoying their 20's, but inside they all have worries. Yoo-Min (Yoon Eun-Hye) still doesn't know what she wants to do. Somehow she gets a job as an assistant to a top writer. Yoo-Min wasn't even sure if she would take the job as an assistant, but after seeing an expensive black mini dress at luxury department store she buys the dress with the writer's credit card and in the process accepts the job. Yoo-Min's job turns out to be more of a babysitter for the writer's twin sons. By chance, Yoo-Min runs into high-school acquaintance Young-Mi who also works as a writer's assistant.
