He is one of the idols who shot 300 commercials before his music debut as a member of Super Junior, which he attracted a lot of attention for his pretty boy image.His first acting role was in teen drama Sharp 2 alongside bandmate Kibum on 2005 before the debut of Super Junior.

Shortly afterwards, he appeared in an episode of the series Loveholic and was a regular MC for the cable music show Show! He also appeared on entertainment programs such as "Heroine 6".

In December 2016, he confessed, He was preparing to debut as Trax main vocalist.

He became a worldwide trending topic on Twitter for four days after the account's creation.

In 2011, he formed a project group with label mate Kim Jungmo of TRAX called M&D (meaning "Midnight and Dawn" or "Miari and Dangae-dong", after the members' hometowns).

They released their debut single, "Close Ur Mouth", in June.

Heechul wrote the lyrics and directed the music video for the song, while Jungmo produced and performed the instrumental.

On February 23, 2007, he debuted as part of Super Junior sub-group, Super Junior-T , performing trot single "Rokuko!!! He appeared as a presenter on SBS music programme Inkigayo as a substitute for Andy of Shinhwa, going on to become a permanent host with Ku Hye-sun (23 April 2006 – 18 February 2007), Jang Keun-suk (25 February - 7 October 2007) and Song Ji-hyo (11 November 2007 – ). Entertainment production of the musical Xanadu, playing the role of Sonny in rotation with bandmate Kangin.

He co-MC 4 straight years the Dream Concert (2008–11). The production ran between 9 September-23 November 2008 at the Doosan Art Center, Yeonji-dong, Seoul.

he didn't participate in any of the stage shows, including the end-of-year award shows For 3 months.

On October 9, he created a personal Facebook account which received 5,000 friend requests within five minutes.

However, plans changed and the company declared a halt in forming future Super Junior generations.