Jung In-sun started out as a child actress and some of her early works are the SBS sitcom Soonpoong Clinic in 1998 and the KBS2 fantasy series Magic Kid Masuri in 2002. In 2003, she became part of the smash hit MBC sageuk Dae Jang Geum and the film Memories of Murder by director Bong Joon-ho. In 2013, she appeared in the tvN period drama Basketball. In 2017, she starred in the KBS2 four-episode series Naked Fireman along with Lee Jun-hyuk. In 2018, she played one of the main characters in JTBC’s Woohoo Waikiki. That same year, she acted alongside So Ji-sub in MBC’s My Secret Terrius, which won her an Excellence Award at the MBC Drama Awards. In 2019, she joined the SBS cooking-variety program Baek Jong-won’s Alley Restaurant, which gave her a Rookie Award and an Excellence Award at the 2019 and the 2020 SBS Entertainment Awards. In 2021, she headlined the web series How To Be Thirty and the SBS musical drama Let Me Be Your Knight.

Jung In-sun attended Sejong University. She previously dated her Woohoo Waikiki co-star Lee Yi-kyung.