2005-2007: Debut with Super Junior

Yesung officially debut as part of 12-member project group Super Junior 05 on 6 November 2005 on SBS's music programme Popular Songs, performing their first single, "Twins (Knock Out)”. Their debut album SuperJunior05 (Twins) was released a month later on 5 December 2005 and debuted at #3 on the monthly MIAK K-pop album charts.

In March 2006, SM Entertainment began to recruit new members for the next Super Junior generation. However, plans changed and the company declared a halt in forming future Super Junior generations. Following the addition of thirteenth member Kyuhyun, the group dropped the suffix "05" and became officially credited as Super Junior. The re-polished group's first CD single "U" was released on 7 June 2006, which was their most successful single until the release of "Sorry, Sorry" in March 2009. In the fall of 2007, the group released their second official album, Don't Don, which became Super Junior's best-selling album and Korea's second best-selling album of the year.

From September 2006 to September 2007, Yesung was host for radio program, M.I.R.A.C.L.E for You, where members of Super Junior often appeared as guests. However, before the radio show's first anniversary, Yesung left in order to concentrate on Super Junior's second album, Don't Don. The last air date for the radio show was 8 September 2007. In November 2006, Yesung, along with members Ryeowook and Kyuhyun, formed Super Junior's first subgroup, Super Junior-K.R.Y, a group specializing in R&B ballads.

In 2007 Yesung became a member of Super Junior-H. He debut as an actor on 26 July 2007 with the release of Attack on the Pin-Up Boys, a high school comedy starring fellow Super Junior members. He played the school's rock star who gets attacked by a mysterious force.