"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. Hye-Ji (Park Han-Byul) is busy playing around and living the life of a socialite. One day, she is scouted by a talent agency. She then becomes the face for a high profile ad campaign and shoots to stardom. Her other 3 friends become jealous of her. Soo-Jin (Cha Ye-Ryeon) holds the most jealousy over Hye-Ji's sudden fame, because she has tried unsuccessfully to become an actress. Soo-Jin has failed many different auditions. Compounding her problems, her father's business has gone bankrupt. Min-Hee (Yoo In-Na) has rich parents, but her parents got divorced. Min-Hee now wants to study abroad, but her poor English skills holds her back.
Ha-neul (Jang Na-Ra) is a gifted violonist who stays at home mostly. Bada ([[Juni (actress)|Juni) was abandoned by her parents. Jin-kyu (Yu Ah-In) lost his parents at an early age and now delivers pizza. Through music, friendship, and love these three friends will learn lessons on life.
The movie chronicles the lives of a group of friends — five young women — a year after they graduate from high school, showing the heartbreaking changes and inspiring difficulties they face in both their friendships and the working world.