2014–2016: Career beginnings with U-KISS On May 15, 2014,
NH Media announced new member Jun to the public via
U-KISS's official Korean website. On June 2, 2014, Jun made his debut with U-KISS and the group released its 9th mini album
Mono Scandal along with the 19+ rated music video of the album's title track "Quit Playing". In the same year, U-KISS also released their 9th Japanese single album
LOVE ON U and kicked off
U-KISS JAPAN LIVE TOUR 2014, which was held in
Nippon Budokan, effectively starting Jun's career in Japan. In December 2014, U-KISS made another comeback with their 10th Japanese single album
Sweetie. In 2015,
U-KISS started the year with 10th mini album
Always, followed by their 4th Japanese regular album
Action in March and 11th Japanese single album
Stay Gold in September. In 2016, U-KISS made another comeback with 12th Japanese single album
Kissing to feel, 5th Japanese regular album
One Shot One Kill, 11th mini album
Stalker, and 13th Japanese single album
PaNiC!. Unfortunately, the 11th mini album
Stalker was the last Korean comeback Jun had with U-KISS until his contract ends in 2021, since
NH Media decided to focus on Japanese market entirely.
2017–2021: UNB and acting breakthrough In 2017, Lee debuted as an actor in the
tvN Wednesday-Thursday drama
Avengers Social Club. It was based on the webtoon titled "Buam-dong Avengers Social Club" by Sajatokki, serialized on
Daum. He played the role of Lee Soo-gyum, a third-year student at Saebit High School and the youngest member of the Bokja Club. Lee Soo-gyum was the illegitimate child of Lee Byung-soo (played by
Choi Byung-mo) and he had a decisive role in leading Kim Jung-hye (played by
Lee Yo-won) to form the Bokja Club. He was also the actual brain behind the Bokja Club, and he joined the club to take revenge on his father, who used him to secure the company's succession. On October 28, 2017, Lee joined the survival program
The Unit. During the audition, he performed "Dang Dang Dang", a hip-hop rap song by
Supreme Team, and received the first Super Boot evaluation on the show from the audience. He was ranked 6th in the first week, 3rd in the second week, and 2nd in the third week of the interim ranking result. However, on the first official ranking announcement, he took the 1st rank and was consistently holding the rank thereafter. In the final announcement, he was ranked 1st of the Top 9, debuting as the center. He also made it to 3rd place on the Non-Drama Performers Category list by
Good Data Corporation during the show's final week. He then promoted with
UNB, which consisted of finalists from the show, from April 7, 2018, to January 27, 2019. From April to May 2018, Lee appeared as "Compass" on
MBC's TV program
King of Mask Singer. In the first round, he performed a duet with Lee Sang-hoon of "It Was Like That Then". For the second round, he performed a solo cover version of "Eraser". In May 2018, he made his second acting appearance as Han Min-soo in the MBC television series
Goodbye to Goodbye (2018) and received a Best New Actor award at the
2018 MBC Drama Awards. On April 10, 2019, Lee released his first Japanese solo single "Phenomenal World", which explored the futurepop genre. He performed his first solo showcase in Tokyo on February 4. Prior to the release, he also held a series of concerts on April 6 in Osaka and April 8 in Tokyo. Tower Records Japan ranked "Phenomenal World" as the #7 best-selling Japanese single by a Korean artist for the first half of 2019. He then starred in the
OCN television series
Class of Lies, which aired from July 17 to September 5. On November 6, he released both a Korean and Japanese version of his solo single "My Way", for which he wrote the lyrics. The single featured rapper Reddy and was produced by Sway D, accompanied by two music videos. After a digital download was released on October 30, the Japanese version ranked #2 on the dwango.jp K-POP Life Weekly Singles Chart. On November 28, he released his first Korean solo single "TELL" composed by himself as a pre-release for his album
Gallery. On December 5, he made his solo debut in Korea with the title track "Curious About U" and the single album
Gallery. In 2020, Lee released his first solo Japanese mini album “
22” on January 22, which was also his birthday. In this album, he tackles six songs with different expressions, from softly sung ballads to stylish rap songs and mature dance numbers. He showed off his vocal ability with the ballad "Circle of Love" and sharp movements with the cool singing and dancing in "Come Alive". He also showcased his composing ability with “Gravity”. Also in 2020, he acted in the musical
Swag Age: Shout out, Chosun! and received a Best New Actor award at the fifth
Korea Musical Awards. In April 2020, he played Kang Woo-won in the
SBS drama
Good Casting (2020), which was entirely pre-produced. In June 2020, he made a special appearance in the SBS drama
Backstreet Rookie as a high school student who stole a college student's overcoat to buy cigarettes. In October 2020, he acted in the
MBC Every 1 drama ''
Please Don't Date Him''. He participated in the soundtrack for the drama with the single "To you who will be tired". On October 7, he released his new Korean single "Amen", which explored his interest in rap and hip-hop. In May 2021, Lee starred in the
KBS2 drama
Imitation (2021) as Kwon Ryok, a talented idol-actor and center of fictional idol group SHAX. As a SHAX member, he participated in the songs "MALO", "AMEN", and "Your Sign (SHAX ver)". In the first two mentioned songs, he mainly took over the rap. As Kwon Ryok, he participated in the song "Your Sign" with the cast and "My Old Story" sung in duet with
Jiyeon of
T-ARA. All the songs are available on various music streaming services. After departing NH Media in August, Lee announced in November that he co-founded a new company, J-flex, which will serve as his current agency for his acting projects. In August 2021, he appeared in the third episode of the
Netflix series
D.P. as deserter Jung Hyun-Min. In order to digest the intense action scenes, he learned boxing with actor
Jung Hae-in, who played Ahn Jun-ho in the series, for a few months at an action school before filming. As the action scenes were shot without a stunt double, he received praise for his swift and accurate movements. In November 2021, he starred in the
SBS drama
Let Me Be Your Knight as Yoon Tae-in, a songwriter and vocalist of fictional band LUNA. As a member of LUNA, he sang several songs: "Beautiful Breakup", "Midnight Fantasy", "Let Me Be Your Knight", "Love Paranoia", and "Rock & Roll Tonight". He also sang a song titled "Love One Day" by himself.
2022–2024: Rising popularity In February 2022, Lee starred in the
Netflix movie
Love and Leashes, an adaptation of the webtoon titled "Moral Sense" on the topic of BDSM. He starred alongside
Seohyun (Jung Ji-woo) as Jung Ji-hoo, a newly transferred assistant manager from the business team. Outwardly, he is a nice and popular superior, but inwardly, he hides secret desires. He also sang an OST titled "A Fine Day" for this drama. In 2023, Lee starred in the movie
Brave Citizen, based on the webtoon of the same name. He starred alongside
Shin Hye-sun (So Si-min) as Han Su-gang, a high school bully that's described as a vicious villain that has never been seen before. The filming period was from December 30, 2021 to April 5, 2022 and the movie became available in theaters starting from October 25, 2023. In August 2023, he appeared as the villain in the fourth episode of the
Netflix series
Mask Girl. His acting in
Brave Citizen and
Mask Girl earned him the Best Acting Performance Award at the
2023 Asia Artist Awards. In January 2024, Lee starred in the
Netflix movie
Badland Hunters alongside
Ma Dong-seok,
Lee Hee-joon, and
Roh Jeong-eui. In February 2024, he starred in the
Disney+ series
The Impossible Heir alongside
Lee Jae-wook. In the same month, he starred in the
Netflix series
Melo Movie as Hong Si-jun, an aspiring musician who met Son Ju-a (
Jeon So-nee) again, his ex-girlfriend of seven years. He showcased his singing skills by performing the OST titled "Under Sunset" entirely in English. In March 2025, Lee starred in a supporting role as Park Young-beom, the first love of
IU's character Yang Geum-myeong, in the
Netflix series
When Life Gives You Tangerines. He was recognized in the buzzworthy Drama Performer Category by
Good Data Corporation, ranking 4th in the third week of March and 8th in the fourth week. He also appeared in the Netflix series
Weak Hero Class 2 as antagonist character Geum Seong-je, which aired on April 25. At the 2025
Fundex Awards, he received a double nomination in the Best Supporting Male Performer on OTT Category for his role in those two works, and eventually won it for his role in
Weak Hero Class 2. Lee received praise for his role in multiple romance works, earning him the title of "Romance Master". His ability to seamlessly transition between genres and roles, including villainous characters in recent years, showcased his versatility as an actor. Critics hailed his performance as a "rediscovery of Lee Jun-young's talent". Due to his frequent appearances in OTT series, he is sometimes referred to as "OTT Prince", "OTT Son", or "OTT Civil Servant". Lee then starred in the
KBS2 drama
Pump Up The Healthy Love (2025) alongside
Jung Eun-ji as Do Hyeon-jeong, a gym manager who transformed his life through exercise despite being born smaller than the size of a 1.5-kilogram dumbbell. For this role, he won the Excellence Award, Actor in a Miniseries from the
2025 KBS Drama Awards. Since the album consisted of various genres such as dance, ballad, and hip-hop, its 180-degree different charms proved his limitless musical spectrum and ability as an all-rounder. From August to October 2025, Lee appeared in the
MBC TV variety show
Hangout with Yoo for its ’80s Seoul Music Festival project. He appeared in the episodes that built up towards the festival’s climax, with key episodes including the song selection and performance broadcasts. During the festival, Lee delivered a standout live rendition of the classic song "I MISS YOU". He drew widespread praise from audiences and fellow cast members alike, while viewers loved his energetic performance and stage presence. He secured both the Grand Prize (judged by industry seniors) and the Popularity Award (voted by netizens) on the show. He also rose to 4th place on the Non-Drama Performers Category list by
Good Data Corporation, reflecting the strong public response to his performance and overall presence in the project. ==Personal life==