2005–2011: Beginnings as a child actor In 2005, Yeo made his debut at the age of eight in the film
Sad Movie. He auditioned for the role of Park Hwi-chan and was chosen among 150 candidates despite having no previous acting experience. In 2006, he appeared in his first television drama
I Want to Love, playing a sickly child of a single mother; followed by his first role in a
sageuk drama
Yeon Gaesomun as young Kim Heum-soon. In 2008, he played the younger version of the lead roles in the series
Iljimae and
Tazza. He won his first acting award as Best Child Actor at the
SBS Drama Awards for both dramas. In 2010, he starred in the drama
Giant as the younger counterpart to
Lee Beom-soo's character. According to Yeo, this was the first time he fully immersed himself in a role and began taking acting seriously. In 2011, he played the younger part of the title character in the historical drama
Warrior Baek Dong-soo. He also made a brief appearance as teenage Ddol-bok in the drama
Deep Rooted Tree. 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.
2012: Rising popularity 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. The drama surpassed 40% in ratings and gained "national drama" status. This was followed by a well-received turn in melodrama
Missing You. He won Best Young Actor at the
2012 MBC Drama Awards for his portrayal in both dramas.
2013–present: Transition to lead roles In 2013, Yeo starred as the titular character in action thriller
Hwayi: A Monster Boy, for which he garnered praises and won several Best New Actor honors from annual award ceremonies such as
Blue Dragon Film Awards and
Korean Association of Film Critics Awards. He is the youngest male actor to receive the Best New Actor award in the history of
Blue Dragon Film Awards, at the age of sixteen. In the same year, he was also cast in the sitcom,
Potato Star 2013QR3 as an aspiring mobile application developer. In 2015, he starred in the film
Shoot Me in the Heart, based on the bestselling novel of the same name by Jeong Yu-jeong. He had his first leading role on television with teen vampire series,
Orange Marmalade, based on the webtoon
of the same name. He won Best New Actor Award at
2015 KBS Drama Awards for his role. In the same year, he appeared in the
Korean War film,
The Long Way Home. Veteran actor
Sul Kyung-gu, his co-star in the film, strongly recommended Yeo for the role of Yeong-gwang, and only signed the movie contract once Yeo's casting had been finalized. In 2016, Yeo played the role of
King Yeongjo in the
SBS drama
The Royal Gambler, and won an Excellence Award at the year end
SBS Drama Awards. In 2017, Yeo starred in
tvN's science fiction drama
Circle, and historical movie
Warriors of the Dawn, both of which premiered in May. He was also cast for a special appearance in the star-studded film,
1987: When the Day Comes, based on the
June Democratic Uprising. The movie reunited him with Director
Jang Joon-hwan and actor
Kim Yoon-seok of
Hwayi: A Monster Boy. In July, he starred in SBS's romance drama
Reunited Worlds. In 2018, Yeo was cast in the romantic comedy
My Absolute Boyfriend, based on the
Japanese manga series of the same name. It aired on
SBS the following year. In 2019, he starred in
tvN's remake of the 2012 Korean film
Masquerade, titled
The Crowned Clown, playing dual roles as clown Ha-seon and
King Yi Heon for which he received the nomination for the
Best Actor - Television at
55th Baeksang Arts Awards. The drama was a commercial success, recording the highest ratings in its timeslot throughout its run. 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. In 2021, Yeo starred in the
psychological thriller drama
Beyond Evil directed by
Shim Na-yeon alongside
Shin Ha-kyun as the main leads which premiered in February and aired on
JTBC.
Shin Ha-kyun and Yeo previously appeared in the film
No Mercy for the Rude (2006) where Yeo played the younger version of Shin's character. And in June 2021, Yeo was confirmed as an MC for
Girls Planet 999 which aired on
Mnet in August. In 2022, Yeo starred in the
tvN fantasy-melodrama
Link: Eat, Love, Kill as a sous chef at a high-end restaurant. Later that year, Yeo made his return to the big screen after five years with
Ditto, a remake of the
2000 film of the same name. In May 2023, Yeo signed with J-Full Entertainment. In 2024, Yeo portrayed a terrorist and plane hijacker in 2024 disaster film
Hijack 1971, which marked his first villainous role in his 19-year career; the events of the film was based on a
real-life plane hijacking incident in 1971 when the relationship between North Korea and South Korea became fraught with tensions. In an interview with Singapore's national newspaper
The Straits Times, Yeo described it as a challenge to portray an antagonist for the first time in his career and he himself doubted whether he could play it well, but he credited his co-stars
Ha Jung-woo and
Sung Dong-il for helping him to immerse in the role. ==Ambassadorship==