Won Ji-ahn made her acting debut with a guest role in the 2021 Netflix military drama D.P. That same year, she starred in her first film, A Year-End Medley. Due to its popularity, the movie was released on TV in 2022 as A Year-End Medley: Extended Version. She was then tapped as the female lead in the first and second seasons of the web series Hope or Dope, which earned her a Best New Actress nomination at the 2022 Blue Dragon Series Awards. She also joined the main cast of the KBS2 drama If You Wish Upon Me.