Nicknamed "Nation's Little Brother",[2] he went on to play the younger characters of the lead roles in films and television series such as in A Frozen Flower (2008), Giant (2010), Moon Embracing the Sun (2012), and Missing You (2012).

He is known for playing the title character in the action thriller Hwayi: A Monster Boy (2013), for which he won the Best New Actor trophy at the 34th Blue Dragon Film Awards.

The appearance was upon the request of its lead actor Jang Hyuk, who took a liking to Yeo when the latter portrayed his younger version in the drama Tazza.

[12] In 2012, Yeo rose to prominence when he starred in the fantasy-period drama Moon Embracing the Sun, playing the role of a young crown prince.

[25][26] In 2017, Yeo starred in tvN's science fiction drama Circle, and historical movie Warriors of the Dawn, both of which premiered in May.

The movie reunited him with Director Jang Joon-hwan and actor Kim Yoon-seok of Hwayi: A Monster Boy.

[39] The same year, he was cast in Hong sisters' fantasy mystery drama Hotel del Luna alongside IU.

[41] In 2020, Yeo made a special voice appearance in the drama Start Up as Jang Young Shil, the AI speaker.

He also made a live action cameo in the final episode as a start-up owner named Hong Ji Seok.

[42][43] In 2021, Yeo starred in the psychological thriller drama Beyond Evil alongside Shin Ha-kyun as the main leads which premiered in February and aired on JTBC.

[46] In 2022, Yeo starred in the tvN fantasy-melodrama Link: Eat, Love, Kill as a sous chef at a high-end restaurant.