He is best known for his roles in the television series The Heirs (2013), Misaeng: Incomplete Life (2014), Moon Lovers: Scarlet Heart Ryeo (2016), When the Camellia Blooms (2019), and Squid Game 2 (2024).

Known as a prolific Chungmu-ro actor, he has also starred in the films Twenty (2015), Dongju: The Portrait of a Poet (2016), New Trial (2017), Midnight Runners (2017), Forgotten (2017), and Love Reset (2023).

In 2020, Kang received the Baeksang Arts Award for Best Actor – Television and ranked 23rd in Forbes Korea Power Celebrity annual list.

He portrayed Choi Hoon, a popular high school student known for his academic prowess and good looks, beating out 800 other candidates for the role.

Immediately after musical Spring Awakening, he recruited Kim Ha-neul as first actor under Sam Company, an entertainment agency founded in 2010 by Hwang Jung-min and his wife.

He plays the role of Namsan, the youngest son of Yeon Gaesomun of Goguryeo, caught between his two brothers' differing views on negotiation and war.

It was written by playwright Han A-reum and directed by Seo Jae-hyeong of theater troupe Jukdorok Dalinda, which means running until death in Korean.

Kang, double cast alongside Jeon Sung-woo, played the role of Hermann, the second son and a painter with a crucial clue to the case.

Despite the difficulty, Kang was proud to transform from the Balladeer into Oswald on stage, a role that brought him a sense of accomplishment not found in other shows.

[33] Kang later back to the small screen, starring in the television dramas To the Beautiful You (2012), where he appeared as Min Hyeon-jae, a high jumper, and developed a rivalry with the male lead.

[34] In 2013, Kang was chosen to portray the lead character Jeong Seon-woo in the cable channel Mnet's music drama Monstar, directed by Kim Won-seok.

In his quest to uncover the unjust circumstances surrounding a woman's sudden death, he portrayed the anguish caused by the caste system in the Joseon Dynasty.

Kang's portrayal of Jun-kyung in the drama was showcasing his talent through nuanced facial expressions and emotional depth, effectively conveyed the character's inner conflict and grief.

Kang portrayed the charismatic tsundere Lee Hyo-shin, the son of the Prosecutor General, the student council president and Broadcasting club of Imperial High School.

[38][39] The Heirs became incredibly popular, achieving a peak rating of 28.6% locally and accumulating over one billion views on the Chinese streaming website IQIYI.

[24] In 2014, Kang returned with the 20-episode series Angel Eyes, where he played the role of teen Park Dong-joo, with Lee Sang-yoon portraying the adult version.

[5][42] Kang worked together once again with director Kim Won-seok in his series Misaeng: Incomplete Life as Jang Baek-gi, who joins Steel Team as permanent employee at One International.

[44][45][46] In 2015, Kang was deeply honored to have the opportunity to make his debut in a two-hander play alongside the esteemed senior actress Park Jeong-ja.

[55][56] Due to his commitment to appear at the Blue Dragon Film Awards, Kang initially thought he couldn't join the Youth Over Flowers trip.

[63] In 2017, Kang starred in the film New Trial, acting as a young man who spent a decade in prison after an abusive investigation for a crime he did not commit.

[64] He then starred alongside Park Seo-joon in the action comedy film Midnight Runners, playing a nerdy student of the Korean National Police University.

From November 30 to December 12, 2019, the trio embarked on a two-week journey in Argentina, immersing themselves in the stunning landscapes and vibrant culture of the country.

[80] In 2021, Kang made his comeback to the silver screen with Waiting for Rain, playing the role of Young Ho, a man who lives his life aimlessly while exchanging letters with his lover.

[81] The same year he was confirmed to star in the mystery thriller film Streaming in which Kang's character runs a popular YouTube channel based on criminal profiling.

[88] On October 3, 2023, the romantic comedy film Love Reset, directed by Nam Dae-jung, was released in theaters in South Korea.

[91][92] The success of the drama Monstar brought more endorsement offers,[36] including a "Love Taste" commercial with Ha Yeon-soo for Danish Drinking Yogurt.

He featured in commercials for Yogiyo delivery app with Park Shin-hye,[95] Nongshim Ramen with Hyeri,[96] Buckaroo Jeans with Seolhyun,[97] and Daeng Gi Meori Shampoo.

[107] In 2017, he expanded his portfolio to include endorsements for Kayak flight booking site,[108] Parkland men's suits,[109] and Socar car sharing service.

In 2019, he collaborated with Jeong Yeo-been for the Wadiz crowdfunding platform[112] and featured in CJ CheilJedang's instant rice advertisement alongside child actor Kim Jun.

[117] In 2021, Kang became the face of Corel kitchen appliances and financial services with NH Nonghyup Bank, partnering Han So-hee.