She attended the Campbell Hall School in Los Angeles. Mary-Kate and Ashley attended New York University's Gallatin School of Individualized Study, beginning in 2004.
She and her twin sister became household names and a popular figures in the preteen market during the late 1990s and early 2000s, with her likeness seen in clothes, books, fragrances, magazines, movies, and posters, among others. There were fashion dolls of her made by Mattel from 2000 to 2005. They also starred in the films Getting There (2002), When in Rome (2002), The Challenge (2003) and made cameos in Charlie's Angels: Full Throttle (2003). In 2004, the twins appeared in the theatrical light-hearted romantic comedy, New York Minute.
In 2004, both Ashley and Mary-Kate Olsen became co-presidents of their company Dualstar (created in 1993 following the success of Full House), the brand currently selling in over 3,000 stores in America and 5,300 stores worldwide.
In 2004, they made news by signing a pledge to allow all the workers that sew their line of clothing in Bangladesh full maternity leave. The National Labor Committee, which organized the pledge, later praised the twins for their commitment to worker rights.