Taemin was discovered at the 2005 S.M. Open Weekend Audition Casting. In 2008, he was chosen as a member of the group Shinee, the 5-member boy group. The group debuted on May 25, 2008 on SBS's Inkigayo."
On September 19, 2012, Taemin released his first OST, "U", for the drama To The Beautiful You. On October 16, 2012 it was announced that Taemin, alongside Super Junior's Eunhyuk and Super Junior-M's Henry, Girls' Generation's Hyoyeon, and EXO's Kai and Luhan would participate as a 6-member dance team for the Veloster theme song, "Maxstep", the collaboration album between SM Entertainment and Hyundai. A video teaser of the song shown at the PYL Younique Show on October 17, 2012. In 2013 he featured in Super Junior-M's Henry solo song "Trap" alongside Super Juniors's Kyuhyun. 
On July 25, 2014 it was announced that Taemin would be making his official solo debut in August. The official music video for his title song "Danger" came out on August 15th. On August 18, Lee Taemin released his solo mini album "Ace" which contains six songs.
In December 2011, Taemin took part as a voice actor for the Korean animated movie called The Outback as the main character, Johnny, a white koala turned hero, along with fellow labelmate, Girls' Generation's Sunny.
Taemin studied Chinese in Beijing in 2007. In March 2011, he transferred to Hanlim Multi Arts High School from his previous school, Chung Dam High School to accommodate his hectic schedule for Shinee’s Japanese advancement. He graduated in February 2012, but was unable to make it to the ceremony due to Shinee activities.