D.O. was born in Goyang, Gyeonggi Province, South Korea, on January 12, 1993. He went to Goyang Poongsan Elementary School, Baekshin Middle School, and Baekseok High School. He has an older brother, Do Seungsoo, who is 3 years older than him. D.O. began singing in primary school and was an avid participant in local singing competitions throughout his high school career.

In 2010, he was advised to audition for S.M. Entertainment after winning a local singing contest. He subsequently became an S.M. Entertainment trainee during his last two years of high school. He performed Na Yoon-kwon's "Anticipation" and Brown Eyed Soul's "My Story" at his S.M. audition.

D.O. was formally introduced as the eighth member of EXO on January 30, 2012. The group officially debuted on April 8 with the extended play Mama. In July 2013, he was featured in the song "Goodbye Summer" from f(x)'s second studio album Pink Tape. In December 2013, D.O., along with fellow Exo members Baekhyun and Chen, sang the title track for the group's second EP Miracles in December.

In September 2014, D.O. made his acting debut with a supporting role in the movie Cart, playing a high school student and son of a grocery store worker and union member (played by Yum Jung-ah). The movie premiered at the 2014 Toronto International Film Festival. He also released an original Soundtrack titled "Crying Out" for the movie. Later in 2014, D.O. made his small screen debut playing the supporting role in the SBS drama It's Okay, That's Love, which starred Gong Hyo-jin and Jo In-sung. D.O. was praised by film critic Heo Ji-woong for his performance in the series, and was later nominated for the Best New Actor award at the 51st Baeksang Arts Awards.

In June 2015, D.O. featured in KBS's drama Hello Monster, playing a psychopath. In November 2015, D.O. was nominated for the Best Supporting Actor award at the 52nd Grand Bell Awards for his role as Tae-young in Cart.

In January 2016, D.O. was announced as one of the cast of voice actors for the feature-length animated film The Underdog, which is slated to premiere in 2018. He will voice Moongchi, a stray dog who is separated from his owner. In February 2016, he collaborated with Yoo Young-jin on a duet titled "Tell Me (What Is Love)" for S.M. Entertainment's Station music project. He had previously performed a short version of the song as a solo performance throughout Exo's first concert tour. Later in February, D.O. starred as the male lead alongside Actress Kim So-hyun in the romantic film Pure Love. In October 2016, D.O. starred alongside Chae Seo-jin in Positive Physique, a web drama produced by Samsung. The series became the most watched web drama of all time. In November 2016, D.O. starred alongside Jo Jung-suk and Park Shin-hye in the film My Annoying Brother, playing a national level Judo athlete. D.O. and Jo Jung-suk also recorded the ending theme song, titled "Don't Worry", for the movie. D.O was awarded the Blue Dragon Film Awards a year later for his performance in the film.

In 2017, D.O starred in the comedy thriller film Room No.7. The same year, he starred in Kim Yong-hwa's film Along With the Gods: The Two Worlds, a blockbuster adaptation of the same-titled webtoon about a court in the afterlife where the deceased undergo multiple trials for 49 days.

In 2018, D.O is set to star in Swing Kids, a film set in a concentration camp in North Korea during the Korean War. He plays a North Korean soldier who falls in love with tap dancing in the midst of all the chaos. The same year, he was cast in his first small-screen leading role, playing a crown Prince in Dear Husband of 100 Days.