Go Ah-sung made her acting debut in the 2004 KBS children’s show Oolla Boolla Blue-jjang. In 2006, she debuted in the big screen with a starring role in director Bong Joon-ho’s blockbuster monster film The Host. Her performance in the movie won her numerous awards, including the Best New Actress at the 27th Blue Dragon Film Awards. In 2010, she scored nominations for Best New Actress at the Baeksang Arts Awards and the KBS Drama Awards for her work in the teen series Master of Study. In 2013, she starred in the sci-fi action film Snowpiercer, in which she scored several Best Supporting Actress nominations. In 2016, she became part of the SBS black comedy drama Heard It Through the Grapevine, which won her Best New Actress at the 51st Baeksang Arts Awards. In 2017, she headlined the MBC workplace romantic comedy Radiant Office, opposite Ha Suk-jin. In 2020, she appeared as one of the leads in the movie Samjin Company English Class, which was hailed Best Film at the 57th Baeksang Arts Awards.

Go Ah-sung has two older sisters and has a great interest in photography. Some of her photographs were showcased during the 5th annual Seoul Open Art Fair in 2010.