[12] When Leeteuk traveled to Apgujeong-dong to sightsee in early 2000, a talent scout approached him and recommended he audition for SM Entertainment's Starlight Casting System.

[19] Leeteuk officially debuted as part of the 12-member project group, Super Junior 05 on November 6, 2005, on Seoul Broadcasting System's (SBS) music program Popular Songs, performing their first single, "Twins (Knock Out)".

[22] Originally, the band was meant to have rotational line-ups, much like the Japanese girl group Morning Musume, but the idea to form new generations of Super Junior was dropped after fans objected.

[30][31] A year later, Leeteuk became a member of Super Junior-H, a subunit focusing on bright and cheerful music, in contrast to the genre of the songs released by the core group.

[34][35] He made his first film appearance with Super Junior members in Attack on the Pin-Up Boys in 2007, playing the role of the school's panda mascot.

[37] This eventually landed him his first solo hosting act on the reality show Leeteuk's Love Fighter, which aired on the cable television channel Mnet in 2008.

[48] In October 2009, when Boom enlisted for mandatory military service, Leeteuk took over his role and the segment's name was changed temporarily to Teukigayo, or Teuk's Academy.

[49] As of the April 10, 2012, broadcast, following the change in MCs and the departure of Shindong from Strong Heart, the show was re-vamped with Leeteuk and Eunhyuk billed as two of the 'six-fixed guests'.

[50] In 2010, he appeared as one of many hosts of Waving the Taegukgi  [ko], a special program to support the South Korea national football team at the 2010 FIFA World Cup.

[51] In the same year, he became the new host for MBC's Enjoy Today,[52] replacing Big Bang's Seungri who left the program to focus on his band's new album.

[66] The film, which documented the singers' journey and experience during the SM Town Live '10 World Tour concert at Madison Square Garden in New York, was theatrically released on June 21, 2012.

[75] He took part in a photoshoot documenting the shaving of his hair for the male fashion magazine Geek before his enlistment, and was featured on the cover of its December 2012 issue.

It ran from January 9 to 20 at the National Theater of Korea, co-starring actors Ji Hyun-woo, Kim Mu-yeol, Jung Tae-woo, and singers Yoon Hak of Supernova, and Lee Hyun of 8Eight.

[90][91] He returned as a television presenter becoming the special MC in episode 783 of Inkigayo with Heechul and Lee Yu-bi, standing in for Baekhyun, Suho and Kwanghee who had conflicting work schedules.

[104] He had participated previously as a competitor in the series with other members of Super Junior in the 2010 and 2011 editions, during which he infamously disqualified himself during the 110 metres hurdles race in both competitions.

[116] A week after he hosted his first Idol Star Athletics Championships in 2015, he appeared as the presenter on Mnet's new mystery music game show, I Can See Your Voice alongside Yoo Se-yoon and Kim Bum-soo.

[123][124][125] He appeared as host of several other programs in 2015 like Match Made in Heaven Returns [ko] with Lee Hwi-jae, a reboot of 2002 program Kang Ho-dong's Match Made in Heaven,[126] White Swan with Lee Seung-yeon,[127] The Mickey Mouse Club with SM Rookies as the Mouseketeers,[128][129] and episode 782 of Music Bank, filling in for Park Seo-joon.

[132][133] He made a cameo appearance as a music show host in episode 5 of television drama Persevere, Goo Hae-ra which aired in March 2015.

[152] He was slated to co-host Star Coming, a South Korea-China joint program in late 2016, but its production was abruptly cancelled following rising tensions between the two countries.

[153] His roles in the industry earned him the top three spots on the Idol MC of the Year list published by My Daily news portal.

[154] The journalist in charge of the list, Lee Seung-gil, praised him for his unique ability to make his guests or his co-hosts to stand out and considered him a "professional MC".

[154] He moved out of his comfort zone of studio work by becoming the MC of 7 First Kisses' press conference,[155] and the preview screening of the documentary film See-Saw.

[156][157] On top of that, he became a public speaker through SM Entertainment's cultural lecture series, The Moment, which featured lecture collaborations between SM artists and experts in various fields with the theme "Healing the wounded 2016 and welcoming the year 2017 happily":[158] partnering with chef Lee Won-il for the lecture entitled "The Single Man's Lifestyle" in February 2016;[159] with a mental health specialist, Yang Jae-jin for "Healing Counseling for Young People" in May;[160] with Kim Ji-yoon, director of the Institute for Good Relationships for "Love and Romance" in September;[161] and "Leeteuk's Unique Day with Webtoon Writer Lee Jong-beom" in December.

[162] Leeteuk embarked on his first solo Asia fanmeeting tour, Star;Teuk, making stops in Shanghai, China, in September,[163] and Taipei, Taiwan, in December 2016.

[168][169] He took part in several variety shows throughout the year including Hard Workers,[170] as a courier in We Have Delivery,[171] as a detective in Sherlock's Room,[172] and as a celebrity mentor in Fearless Guys.

[173] As an actor, he made a cameo appearance as a radio DJ in episode 7 of the television drama Borg Mom [ko], which aired on October 27, 2017.

[192] After his appearances on the program, he was cast in the variety show Sell to Return, a collaboration with Thai and Malaysian home shopping channels.

[203] He starred in a YouTube Original series Analog Trip with fellow band members, Eunhyuk, Donghae and Shindong, as well as TVXQ's Yunho and Changmin in September 2019.

[234] On April 19, 2007, almost two months after Super Junior-T's release of their first single "Rokkugo", Leeteuk was seriously injured in a car accident with Shindong, Eunhyuk, Kyuhyun, and two managers.

[239] Because of the accident, Leeteuk made only a minor appearance in Super Junior's debut big-screen production, Attack on the Pin-Up Boys in 2007.