Kim Jong Kook first entered the Korean music industry in 1995 as a member of the group Turbo, which became immensely popular for their catchy music. After the group disbanded a few years later, he became a solo singer in 2001, mostly concentrating on ballads. Although his unusually high tone of voice is often joked about (with many stars jokingly calling it a "mosquito voice"), he has had many hit singles and has also been a frequent guest on many variety shows, most notably X-Man. In addition, his muscular body is often considered one of the best in K-pop, due to constant weight training.

Kim Jong Kook had a big slump after Turbo; however, he made a huge comeback with his second album. One of the songs in the second solo album called Han Namja (One Man) was the reason for all his success. Furthermore, a scandal rumor with Yoon Eun Hye grabbed much attention. This rumor started because both were permanent members of a famous variety show called X-Man. This rumor brought them close, and they started acting like a couple in X-Man.

By 2005, Kim Jong Kook became one of Korea's most popular artists; his third album sold in excess of 300,000 copies, making it one of the year's best-selling albums in Korea. He capped off that year by sweeping the 3 Daesang Awards from all 3 major TV stations. In doing so, he became only the second artist ever to accomplish this feat since Jo Yong Phil in the 1980s. The lead single from the album, "Lovable", topped many charts. It was also included in Pump It Up and Audition Online.

On January 21, 2006, Kim Jong Kook, Jeon Hye Bin, and Im Tae Kyung participated in Thuy Nga's Paris by Night 81 Vietnamese concert in California. Kim Jong Kook performed "To Her Man".

In March 2006 Kim Jong Kook received his military service enlistment letter at the height of his popularity and career. Kim also released his fourth album around this time, unable to directly promote it while in the military, he used unorthodox methods. To comply with Korean law, the music video was shot so that his face would never be seen on screen. Also, in order to raise awareness, Kim Jong Kook's rumored girlfriend Yoon Eun Hye was asked to star in the music video. Though there has been no direct promotion, his fourth album has sold in excess of 100,000 copies. It was announced in late April 2008 that the singer would end his military service on May 23, 2008. On that day, he was greeted by fans, and during his interview, he said that he was "relieved". His fifth studio album was released on October 22, 2008 as "Here I am" with the featuring song as "Today More than Yesterday" and "Thank you." Proving the "tradition" of not being able to rise once again after military service false, Kim Jong Kook made a successful comeback, making one album, one digital single [Happy Virus] and one trot [Ddajo].

Kim Jong Kook also returned to television, becoming a permanent member of variety show Family Outing, part of SBS's Good Sunday lineup and earning popularity, especially with the love scandals between Lee Hyori and Park Ye Jin. Kim Jong Kook's Hoolala CF with Kim Sooro was released on July 2009. He has also posed for many advertisement for clothing. His sixth album was released on January 27, and a preview of the album was released with the song "Don't Be Good to Me." However the title song for the album is titled "This is the Person". The music video for the song included Park Ye Jin who is famous for the "Family Outing Scandal" between Kim Jong Kook, Lee Hyori and Park Ye Jin. His sixth album is titled "The Eleventh Story" because in his music career, he has so far released 11 albums.

On August 27, 2010 Kim Jong Kook received a lumbar micro-discectomy back disk surgery at Seouls Kwan Ahk Goo Chung Ryong Dong Kangnam Choice hospital. Kim Jong Kooks management company, 101 Entertainment, stated, Kim Jong Kook carried on with his daily activities without knowing that he had a ruptured disk. He did feel pain, but didn't think much of it, and he endured his condition with painkillers while filming SBS Running Man.

Kim Jong Kook active participation in SBS Running Man makes him one of the big names in Korean Variety Shows World. He had been called "SpartaKook" and "The Commander" throughout the SBS Running Man and he has received a favorable evaluation leading the mission with his muscular body and extraordinary intelligence. This proved as he won SBS Entertainment Best TV Star Award in 2010 and SBS Entertainment Excellence Award in 2011.