Ellen Mirojnick was born on 7 July 1949 in New York City, the daughter of Abe and Sunny Schneid. She studied at the School of Visual Arts (1967-68) and the Parsons School of Design (1968-70), initially working in junior sportswear design before entering the film industry in 1977 with French Quarter.

She became a frequent collaborator with actor Michael Douglas, designing costumes for Fatal Attraction (1987), Wall Street (1987) - where her work helped define the iconic look of Gordon Gekko - Basic Instinct (1992), A Perfect Murder (1998), Wall Street: Money Never Sleeps (2010), and Behind the Candelabra (2013), for which she won an Emmy. She also built long-running partnerships with directors Jan de Bont and Paul Verhoeven, contributing to films including Speed, Twister, Showgirls, and Starship Troopers. Her other notable film credits include The Greatest Showman (2017) and Oppenheimer (2023), for which she received an Academy Award nomination for Best Costume Design. In television, she has designed for Bridgerton, How to Get Away with Murder, and The Knick.