2006–2010: Beginnings Kang began his acting career in
musical theatre using his birth name, Kim Ha-neul. His stage debut occurred in 2006 at the age of sixteen with the musical
The Celestial Watch, during his first year of high school."It was a transitional period for me. I didn't feel ready for the acting, and I didn't like being thrust into the public eye through the drama. I really wanted to learn more by doing theater. So even as I was auditioning for
My Mom! Super Mom!, I kept wanting to do theater. In the end, after the audition, I called the director and politely asked them if they could let me drop out, as I didn't want to do it." In 2009, Kang, who was cast as an
understudy for musical
Thrill Me, performing the role of Richard on April 10 and 17. That same year, he successfully auditioned for the rock musical
Spring Awakening.
Spring Awakening. From June 30, 2009, to January 10, 2010, Kang played the role of Ernst in
Spring Awakening, appearing in a cast that included
Jo Jung-suk and
Kang Mu-yeol (double cast as Moritz), as well as
Joo Won (as Melchior). Despite cast changes and absences among his colleagues, Kang performed in every show, totaling 266 performances, a challenging yet fulfilling experience for him. That same year, Kang was admitted to the 50th Batch of the Theater Department at
Chung-Ang University. Consequently, his character in
Hometown Over the Hill was written out of the drama's storyline, departing to pursue further studies in
Seoul. Also in 2010, Kang successfully auditioned for
Lee Joon-ik's film
Battlefield Heroes. The film is a sequel to Lee's earlier work,
Once Upon a Time in a Battlefield, and focuses on the Silla–Tang Allied Forces' campaign to attack Goguryeo's Pyongyang fortress. Kang was cast as Namsan, the youngest son of Yeon Gaesomun of Goguryeo, who is depicted as conflicted between his two older brothers' opposing stances on negotiation versus warfare."I'm still grateful to director
Lee Joon-ik for making my first set so beautiful. One day after filming, we were drinking together when he suddenly asked me and [Lee]
Kwang-soo to be friends. I said, "Director, how dare we be friends with you?" He replied, "Why? Foreigners are friends with everyone, even their grandparents and children, so why can't we be friends?" Because of that connection, even after
Battlefield Heroes was finished, I would go to the director's office to hang out and drink with him. It was so nice."Kang also secured a supporting role through audition in the film ''
You're My Pet'' (2011), which starred actress
Kim Ha-neul. He was cast as Yang Young-soo, a musical actor and a friend of the male lead, In-ho (played by
Jang Keun-suk), who is responsible for guiding In-ho in matters of love. In November 2010, he formally adopted the stage name
Kang Ha-neul, replacing his birth name, Kim Ha-neul, to prevent confusion with the actress Kim Ha-neul.
2011–2014: New stage name, film debut, and breakthrough roles in television The year 2011, marked his new beginning as actor under the stage name Kang Ha-neul. He was credited with this new stage name for his debut film,
Battlefield Heroes, which was released in January of that year. In September 2011, Kang appeared as Eunuch Gu-dong in the musical
Prince Puzzle. The production, written by Han A-reum and directed by Seo Jae-hyeong of Jukdorok Dalinda, was notable for being staged within the Sungjeongjeon hall of
Gyeonghuigung rather than a conventional theatre. Kang noted, "I chose this work because I wanted to work hard until I die." Kang initially believed he was being offered the role of the Crown Prince in
Prince Puzzle; Kang described his role as physically demanding. Noticing his exhaustion, the stage manager advised him to read audience reviews for motivation, implying the production's critical success. Director
Lee Joon-ik attended a performance and praised Kang's acting, stating, "You're really good, as expected." In 2012, Kang was cast in the original musical
Black Mary Poppins, produced by
Kim Soo-ro. Written, directed, and composed by Seo Youn-mi, a rising dramatist in
Daehangno, the thriller was inspired by the
Mary Poppins series by
P. L. Travers. The musical centered on a 1930s German mansion fire incident involving four siblings. Kang was double-cast alongside
Jeon Sung-woo as Hermann, the second son and a painter holding a crucial clue to the case. Jung Sang-yoon and Jang Hyun-duk were double cast for the role of Hans. Other cast members included Jang Seung-jo,
Yoon Na-moo, and Lim Kang-hee. In November 2012, Kang participated in the third Korean production of
Stephen Sondheim's
Assassins, performing alongside Hwang Jung-min. For Kang, participation in a Sondheim work fulfilled a long-held dream, despite the challenging nature of the complex melodies and unusual time signatures. He played the dual roles of the Balladeer and Lee Harvey Oswald. The production ran at the Yonkang Hall of Doosan Art Center until February 3, 2013. That same year, Kang also returned to the small screen, starring in the
television dramas To the Beautiful You (2012) as Min Hyeon-jae, a high jumper who develops a rivalry with the male lead. In 2013, he was cast as the lead character Jeong Seon-woo in the
Mnet's music drama
Monstar, directed by
Kim Won-seok. The role required him to learn to play the
cello,
bass guitar, and
contrabass. He dedicated himself to practicing these instruments, sacrificing rest by only sleeping for an hour or 30 minutes. Despite the challenges, he was grateful for the director's faith in him and the praise for his efforts. Following the conclusion of
Monstar, Kang made a special appearance in the
MBC drama
Two Weeks as Kang Seong-jun, the
autistic son of Jo Seo-hee (played by Kang Hye-ok). He then took on the role of Lee Jun-kyung, an illegitimate son of low
yangban status, in the MBC Drama Festival one-act drama
Unrest, which aired on October 3. His character pursued the truth behind an unjust death, allowing Kang to portray the anguish caused by the Joseon Dynasty's caste system. Kang's portrayal was praised for showcasing his talent through nuanced facial expressions and emotional depth, effectively conveyed the character's inner conflict and grief. In July 2013, Kang secured a supporting role in writer
Kang Eun-sook's drama
The Heirs (2013), playing Lee Hyo-sin,
the charismatic tsundere son of the Prosecutor General and the student council president of Imperial High School. He starred alongside
Lee Min-ho,
Park Shin-hye,
Krystal,
Kim Woo-bin,
Kang Ji-won, and
Park Hyung-sik. Kang had his first onscreen kiss scene in the drama.
The Heirs achieved significant achievement, with domestic ratings peaking at 28.6% and accumulating over one billion views on the Chinese streaming platform
IQIYI, leading to widespread recognition for Kang. His first lead role in a feature film followed with the release of Oh In-chun's film
Mourning Grave which was released in theaters on July 3, 2014. The film combined elements of horror, romance, drama, and comedy, set in a rural school. Kang starred as In-soo, a reclusive student with the ability to perceive ghosts, a college friend
Kim So-eun's character. The drama's success led to a surge in Kang's recognition, culminating in him winning the Popularity Award at the 2015 Cable TV Broadcasting Awards.
2015–2018: Theater debut, film success, and military musical In 2015, Kang made his debut in a
two-hander play,
Harold and Maude, alongside veteran actress
Park Jeong-ja. Adapted from
Colin Higgins' novel, the production explores the intergenerational friendship and affection between Harold, a suicidal 19-year-old, and Maude, an 80-year-old embracing death. It had been previously performed in Korea under the title
19 and 80 starting in 2003. Over the years, Park Jeong-ja has consistently portrayed the role of Maude, while the role of Harold has been played by different actors in each production. The 6th Korean production ran from January 9 to February 28 at the Deloreum Theater of the National Theater of Korea. Kang, playing Harold, commented, "I may be disposable, but I will strive to be an unforgettable disposable Harold. I came across this work and Teacher Park Jeong-ja when I needed to study more and wanted to fill the feeling that something was empty. When I heard that Teacher Park Jeong-ja would be appearing, I naturally decided to appear as well. When we read the script together, the really good lines felt like they were being spoken to me by Teacher Park Jeong-ja, so I felt really comfortable when acting." That same year, three of Kang's films were released sequentially. His first
biopic, musical film ''
C'est si bon'' premiered on February 5. The film chronicles the folk music movement centered at the C'est Si Bon music center, which introduced renowned
folk music artists such as
Cho Young-nam, Yoon Hyeong-ju, Song Chang-sik, and Lee Jang-hee. Kang portrayed Yoon Hyeong-ju, a member of the Twinfolio band. Having been exposed to Yoon Hyeong-ju's music through his father, Kang's vocal talent was highlighted as he successfully replicated Yoon's clear, melodious voice and precise enunciation. On March 5, 2015, Ahn Sang-hoon's
period film Empire of Lust, was released. Kang played Jin, the King's son-in-law, a character barred from politics and engaged in hedonistic pursuits. It was his first time filming an intense and violent bed scene, which was a challenging experience. Despite the actress reassuring him that it was just acting, he felt guilty and remorseful afterwards. Shortly thereafter, the
coming-of-age film Twenty, directed by
Lee Byeong-heon, was released on March 25. Kang starred as Kyung-jae, a studious university student aspiring to a corporate career. For his performance in
Twenty, Kang received nominations for Best New Actor at the Baeksang Arts Awards, Blue Dragon Film Awards, and Grand Bell Awards. He subsequently won Best New Actor at the 2015 Golden Cinematography Awards, the Korean Film Actors' Guild Awards, the Korea World Youth Film Festival, and the 2016 Chunsa Film Art Award. Due to his commitment to appear at the
Blue Dragon Film Awards, Kang initially thought he couldn't join the
Youth Over Flowers trip. However, he was surprised by the team and taken right after the award show to join the other actors on November 26, 2015.
Youth Over Flowers Iceland was initially announced with three cast members:
Jung Sang-hoon,
Jung Woo, and
Jo Jung-suk. The quartet traveled to Iceland on November 25, 2015, with a mission to see the aurora before returning on December 4, 2015. In 2016, Kang starred in the
black and white biographical period film Dongju: The Portrait of a Poet, where he played the titular role of poet
Yun Dong-ju. This performance earned him Best Actor nominations at the
25th Buil Film Awards and
4th Wildflower Film Awards. He also appeared in the
romantic comedy film
Like for Likes, playing a young songwriter who suffers a hearing disability. The same year, he co-starred in the
historical drama Moon Lovers: Scarlet Heart Ryeo, portraying the
8th Prince Wang Wook, a role that secured him an at the
2016 SBS Drama Awards. In 2017, Kang starred in the film
New Trial, depicting a young man wrongfully imprisoned for a decade following an abusive investigation. He then co-starred with
Park Seo-joon in the action comedy film
action comedy film
Midnight Runners, playing a nerdy cadet of the
Korean National Police University. The film was a commercial success, becoming the
4th highest-grossing South Korean film in 2017. In the same year, he also appeared in
Jang Hang-jun's
mystery thriller film
Forgotten alongside
Kang Mu-yeol. Kang then went to his
mandatory military service, during which he was selected to appear in the military musical
Shinheung Military Academy. In September 2018, he reunited with actor
Ji Chang-wook and collaborated with
K-Pop idol
Kim Sung-kyu from
Infinite and collaborated with K-Pop idol Kim Sung-kyu (Infinite) in the production. As one of the largest initiatives undertaken by the
Republic of Korea Army, the musical reached a cumulative audience of 110,000 viewers. Kang's portrayal of the character Paldo earned him a nomination for Best Actor at the 7th Yegreen Musical Awards.
2019–present: When the Camellia Blooms, Squid Game, and continued success In 2019, Kang made a comeback to television with the
KBS2 TV series
When the Camellia Blooms alongside
Gong Hyo-jin. He portrayed Hwang Yong-sik, a police officer with a strong instinct for finding and beating up criminals. He moves back to his hometown Ongsan after being demoted. The drama achieved the highest ratings for a miniseries that year, garnering critical acclaim and numerous accolades, including the
Baeksang Arts Award for Best Actor – Television for Kang. He also won several other best actor awards and was ranked second (behind his co-star Gong Hyo-jin) in the
Gallup Korea's Actor of the Year survey. In November 2019, Kang's contract with SEM Company, his agency since 2010, expired. He subsequently joined TH Company, a newly established agency founded by his former manager. Kang then joined the second season of the travel documentary
Traveler with
Ahn Jae-hong and
Ong Seong-wu. From November 30 to December 12, 2019, the trio filmed a two-week journey in Argentina, visiting locations such as
Iguazu Falls,
Perito Moreno Glacier, and
Patagonia. In January 2020, he returned to theater in
Kang Dong-yeon's
Fantasy Fairy Tale, a work that combines a play-within-a-play material, dance, mime, music, and acting. Kang acted as the love clown, a character with a pure and emotional personality. The play ran from December 21, 2019, to March 1, 2020, at Dongduk Women's University Performance Arts Center Cotton Hall. This marking his first stage performance since
Harold and Maude in 2015. In 2021, Kang returned to silver screen with
Waiting for Rain, playing Young-ho, a man who lives aimlessly while corresponding with a lover via letters. He acted opposite
Chun Woo-hee. It was released on April 28, 2021. The same year, he was confirmed to star in the mystery thriller film
Streaming. In 2022, Kang starred in the period adventure film
The Pirates: The Last Royal Treasure, a sequel to the blockbuster hit
The Pirates. The film was released in South Korea on August 6, 2014, by
Lotte Entertainment. It has grossed over $64 million worldwide. Later that year, he starred in the
JTBC series
Insider, playing a judicial trainee who goes undercover in prison to catch a gang leader. Following this, he starred in the drama
Curtain Call, which earned him the Top Excellence Actor Award at the
2022 KBS Drama Awards. On June 24, 2023, it was reported that Kang would join the second season of the series
Squid Game. He was also confirmed to lead the film
Yadang: the Snitch. The romantic comedy film
Love Reset, directed by Nam Dae-jung and co-starring
Jung So-min, was released in South Korea on October 3, 2023. The plot centers on a couple who experience amnesia 30 days before their scheduled divorce. On April 22, 2024, Kang was announced to star in the
Netflix thriller movie
Wall to Wall, directed by Kang Tae-jun. On October 17, 2024, it was reported that Kang will lead
ENA romance drama
Tastefully Yours. In the winter of 2024, Kang appeared as Dae-ho
second season of
Squid Game as
Kang Dae-ho / Player 388. In 2025, Kang had multiple project releases. On March 21, the thriller film
Streaming, written and directed by Cho Jang-ho, was released. Kang starred as a top crime channel
streamer who investigates an unsolved string of serial murders during a live broadcast. This was followed by the film
Yadang: the Snitch, released in South Korea on April 16, 2025, by
Plus M Entertainment. Kang portrayed Lee Kang-soo, a broker known as "Yadang" who manages the drug trade while secretly providing information to law enforcement. His
Netflix thriller film
Wall to Wall, written and directed by Kim Tae-joon, and co-starring
Yeom Hye-ran, and
Seo Hyun-woo, was premiered on July 18, 2025, on July 18, 2025. Kang portrayed Noh Woo-sung, a successful homebuyer from apartment unit 1401, suffering from inter-floor noise issues. == Other ventures ==