At 13, Ren was discovered to model for the label Brandy Melville. She became a social media phenomenon at 15, when photos of her in a black string bikini posing by the pool went viral on Tumblr. Since then she has appeared in a series of advertisements for the mobile game Final Fantasy XV: A New Empire. She launched an activewear line called Ren Active. Ren was named a Sports Illustrated Swimsuit 2018 Rookie of the year. On September 12, 2018, Ren was announced as one of the celebrities who will compete on season 27 of Dancing with the Stars. Her professional partner was Alan Bersten. Ren and Bersten reached the finals and came in fourth place on November 19, 2018.