After her debut as a supporting actress in the 2007 film My Son, she successfully auditioned and landed the part in the sitcom Kimchi Cheese Smile.

[6][7] She then contributed her vocals to "My Fair Lady," one of the tracks in Lee Seung-hwan's 20th anniversary album Hwantastic Friends.

[11][12] She and Moon Geun-young played siblings in the popular modern fairytale retelling Cinderella's Stepsister,[13][14][15][16] but Seo later said she considers it her worst performance, despite being the character she worked hardest on.

[19][20] She next portrayed a calm yet brave art major in the fantasy-horror TV movie Knock, about a magical mask passed down in a shaman family.

[26] On December 12, 2019, Seo was featured in a horror film titled The House and took on the role of a pregnant woman named Eun Bi-roo.