After a relatively short training period of one year and five months, he made his debut as a member of the five-member male group TVXQ through SBS BoA & Britney Spears Special Stage on December 26, 2003.

In July 2009, Park and two of his TVXQ bandmates, Jaejoong and Junsu, filed a lawsuit against their South Korean agency S.M.

In September 2010, JYJ released extended play The..., which debuted at number one on Japan's Oricon album charts.

JYJ promoted the new album via a worldwide showcase tour throughout October and November with dates in South Korea, Southeast Asia and the United States.

The tour was then extended to Europe and South America, adding another four stops in Spain, Germany, Chile and Peru.

For the group's Japanese releases, Park wrote and co-composed "Kiss Shita Mama, Sayonara" (Kissしたまま、さよなら, lit.

[19] He announced his retirement from the entertainment industry in April 2019, following his arrest on suspicion of illegal drug use and the termination of his contract with his agency.

Two months later, Park made his Korean debut as an actor in the hit 2010 KBS drama Sungkyunkwan Scandal.

He portrayed Lee Seon Joon, a wealthy, passionable and studious nobleman, who falls in love with his fellow schoolmate—a woman disguised as a man.

In 2011, he starred in the MBC drama Miss Ripley with Lee Da-hae, Kim Seung-woo, and Kang Hye-jung.

[31] His character as Song Yoo-hyun has him playing a half-Korean, half-Japanese second-generation director who will falls blindly in love with the antiheroine.

At the 2011 MBC Drama Awards, Park won "Best Newcomer" for his role as lead male in "Miss Ripley."

Park's third role was Lee Gak, a Joseon era prince who time-travels 300 years to the present day, and also as Yong Tae-yong, third generation of conglomerate.

On November 7, 2012, Park returned to television by participating in his fourth drama, MBC's Missing You,[32] in which he portrays homicide detective Han Jung-woo who, in the past when he was fourteen years old, was separated from his first love.

He has since achieved a so-called "Grand Slam" by having won trophies from each of South Korea's three major television channels, SBS, MBC, and KBS.

[35] In April 2017, it was confirmed by Park's agency that he was engaged to Namyang Dairy Products heiress, Hwang Ha-na.

[38][39] In 2016 and 2017, Yoo-chun was accused by four different women of sexual assault, but was acquitted after the police ruled it was difficult to prove the use of force, making the charges invalid.

The case was later forwarded to Seoul Central District Prosecutors Office and he was also cleared of all sexual assault charges.

In 2018, "A" filed for a civil suit for damages against Yoo-chun for 100 million won in compensation and requested for his officetel to be seized.

Because Park Yoo-Chun did not send his objection to the proposal within the given two weeks deadline the terms are accepted by default and solidified the amount he must compensate.

In response, Re:Cielo announced that Park's statements were entirely false and that they were preparing a civil damages lawsuit against him due to his breach of contract and defamation of the company.

He was also suspected of attempting to destroy evidence by dyeing and shaving the hair from his body before undergoing the drug test.

[56][57] On July 2, 2019, Park was sentenced to ten months imprisonment, suspended for two years and a fine of 1.4 million won.