EJ Zimmerman is a Korean-American adoptee, born in South Korea and raised in Maryland. After earning her Equity card on the first national tour of Avenue Q, she built a career in regional theatre, playing roles including Nancy in Oliver!, Kim in Miss Saigon, and Reza in Once. She joined the Broadway revival of Les Misérables on July 12, 2016, as a replacement ensemble member and understudy for Éponine. A Korean Cultural Center New York profile states that she made her Broadway debut performing as Éponine. Zimmerman has also originated roles in developmental productions and performed internationally, including an appearance in the musical I Got Fired at the Daegu International Musical Festival in South Korea.