Kim Go-eun made her acting debut in the 2012 film A Muse, in which she bagged several Best New Actress trophies. In 2015, she was cast in the film Coin Locker Girl, in which she was nominated for Best Actress at the 24th Buil Film Awards. In 2016, she landed her first television role in the tvN romantic drama Cheese in the Trap, which earned her the Best New Actress trophy at the 52nd Baeksang Arts Awards. Later in 2016, she starred in the megahit tvN fantasy series The Lonely Shining Goblin along with Gong Yoo and Lee Dong-wook.  She scored a Best Actress nomination at the 53rd Baeksang Arts Awards for her work in the drama. In 2019, she headlined the SBS fantasy romance The King: Eternal Monarch, opposite Lee Min-ho. She was nominated for a Top Excellence Award at the 2020 SBS Drama Awards for her performance in the series.

In June 2016, Kim Go-eun started dating veteran actor Shin Ha-kyun, who was 17 years her senior. They parted ways eight months later.