Ra Mi-ran made her big screen debut in the 2005 psychological thriller Sympathy for Lady Vengeance and has since become a staple in Korean TV and films. In 2010, she played a North Korean defector in the indie film Dance Town, which won her Best Actress at the 15th Busan International Film Festival. In 2013, she was named Best Supporting Actress at the 34th Blue Dragon Film Awards for her appearance in director Lee Jun-ik’s Hope. In 2015, she starred in the adventure drama film The Himalayas, which earned her the Best Supporting Actress trophy at the 52nd Baeksang Arts Awards. In 2015, she joined the cast of the hit tvN series Answer Me 1988. Her scene-stealing performance in the drama scored her a Baeksang Best Actress nomination in 2016. That same year, she received the Best Supporting Actress honors at the KBS Drama Awards for her work in the weekender Laurel Tree Tailors. Also in 2016, she acted alongside Sohn Ye-jin in the period drama film The Last Princess, which gave her another Best Supporting Actress citation at the 53rd Grand Bell Awards. In 2018, she bagged an Excellence Award at the KBS Drama Awards for the fantasy melodrama Miracle That We Met. In 2021, she picked up the Best Actress trophy at the 41st Blue Dragon Film Awards for her leading role in the political satirical comedy Honest Candidate.

Ra Mi-ran studied theater at the Seoul Institute of the Arts.