Mun was born in Seoul. He is the youngest of the three siblings with two older sisters. He attended Daechi Elementary School located in Seoul. When his family moved to the U.S, he went to John Burroughs Middle School located in Los Angeles. Mun spent his years at Parks Junior High School and Sunny Hills High School, both of which are located in Fullerton, California. In 1996 he returned to Korea and joined SM Entertainment as a trainee and was featured as a rapper on label mate girl group S.E.S.’ single “I’m Your Girl” along with Andy. On March 24, 1998, with the stage name Eric, he debuted as leader and main rapper of group Shinhwa with their single “해결사” (The Solver) on KM Music Tank. He stated that their debut album, Resolver, did not perform well and the band almost disbanded. At the time, he thought seriously about giving up and returning to the U.S.

In 2002, Mun and his Shinhwa bandmates had cameo appearance in the movie Emergency 19 Act. In 2003 director Park Sung-soo cast him in a supporting role for MBC’s series Breathless (I Run). In early 2004, he appeared in the drama Phoenix (Bulsae).

Mun gave up his U.S. citizenship in 2003, to be able to serve his military service. He was the first Shinhwa member to enlist for mandatory military service in October 2008. Because of his back injury from the filming of Wolf, Mun served non-active duty after undergoing four weeks of basic training. He was discharged on October 30, 2010.

In 2005, Mun graduated from Dongguk University with a major in Theater and Film.

In 2005, Mun starred in lead role in MBC’s Super Rookie with actress Han Ga-in. It was also broadcast on Fuji Television. It got solid rating in Korea during the broadcast. Super Rookie was also a big hit in Japan after Fuji TV paid ₩2 billion for the broadcast rights in Japan. It was commercially successful in Japan when it was broadcast there. In December 2005, Mun went to promote Super Rookie in Japan, where he was greeted at the airport by a large crowd.

In early 2006, Mun was injured on the set of MBC drama Wolf, resulting in it being pulled off air after four episodes. Mun was injured whilst shooting a scene, near Namdaemun in Seoul, where he was to save co-star Han Ji-min from being run over by a car. The stunt car driver, misunderstanding the instructions given to him, drove at them at 40 km/h and did not stop in front of them as planned.

Shinhwa’s 10th Anniversary concert in March 2008 marked the start of Shinhwa’s hiatus as a group to fulfill mandatory military service. Before his army enlistment, Mun appeared in a period drama for the first time in his acting career with Strongest Chil Woo. With 30 million wons per episode for Strongest Chil Woo, Mun was the highest paid singer-turned-actor in the industry at the time.

After being discharged, Mun’s first project was supposed to be KBS’ action drama Poseidon opposite Kim Ok-bin, set for broadcast in July 2011. However they dropped out when production was halted after the Bombardment of Yeonpyeong incident in November 2010. Instead, he appeared in another KBS drama, Spy Myung-wol with Han Ye-seul in July, playing a Korean wave star who is at the center of a kidnap plot by North Korean agents.

On July 1, 2011, Mun became CEO (with Lee Min-woo as co-CEO) of Shinhwa Company, a joint venture agency for members Shinhwa to perform as a group. The Company manages the group as a whole, whilst members’ individual activities are managed by their respective agencies.

As part of Top Class Entertainment he produced girl group Stellar, who debuted in August 2011 with the song “Rocket Girl”.

In March 2012, Mun reunited with his Shinhwa bandmates for their comeback after four years, under the management of Shinhwa Company. The group released their tenth studio album The Return on March 23, 2012, launched the concerts 2012 Shinhwa Grand Tour: The Return throughout Asia and their first exclusive variety program Shinhwa Broadcast premiered on March 17, 2012, on cable channel JTBC.

Mun’s rap is featured on Brown Eyed Girls’ Ga-in’s digital single “Nostalgia”, released on November 30, 2012.

On February 8, 2013, Shinhwa’s agency announced the group’s 2013 Shinhwa Grand Tour: The Classic to commemorate the group’s 15 years since their debut was revealed. The album’s name called The Classic.

December 2013, Mun’s contract with Top Class Entertainment came to an end. He did not re-sign another contract with Top Class Entertainment and no longer has any running of group Stellar whom he helped the management to produce and promote the original line up.

In March 2014, Mun successfully concluded the 16th Anniversary Concerts with Shinhwa. After several casting offers from KBS, Mun returned to television in August 2014 with the drama Discovery of Love, which reunites him with Jung Yu-mi, who was his co-star in MBC’s 2007 Que Sera, Sera. It was also announced that he had formed his own management company, E&J Entertainment, with his manager of 10 years, Lee Jong-hyun.

In 2014, Eric reportedly had been dating actress and model Na Hye-mi. However neither would confirm the relationship. Their dating resurfaced again in February 2017 and both confirmed their relationship through their agency. After five years of dating, Mun and Na got married on July 1, 2017 in a private church ceremony with family and friends at Youngnak Presbyterian Church in Jung-gu, Seoul.

Despite its average 7% Nielsen rating, Mun and the team of Discovery of Romance received praise for their acting and Mun won a ‘Triple Crown at KBS 2014 Year End Award (Excellent Actor, Best Couple, and Netizen Award). With this win, Mun had won acting awards at all three major Broadcasting Networks. In 2015, Discovery of Love was nominated for the 2015 Rockie Award in the Melodrama category alongside 30 Vies (Canada), EastEnders (UK), Grey’s Anatomy (USA), My Sunshine (China), and Mysterious Summer (Japan). In an 2015 Instiz discussion post about viewers’ favorite drama characters, Mun’s Kang Tae-ha Discovery of Romance stays in top 10 at #6.

Shinhwa followed up with a comeback in January 2017 with Unchanging: Touch as the second part of their 13th album. On March 24, Shinhwa released Shinhwa 18th, their first self-produced variety show through Naver’s paid subscription platform for Vapp+.

In February 2017 Eric and actress Na Hye-mi confirmed their relationship after it was reported in the news. The couple got married on July 1, 2017 at Youngnak Church in Jung-gu, Seoul, South Korea after five years of dating.

In 2018 Eric and Shinhwa had the whole year to celebrate the group’s 20th anniversary since debut with various activities starting with a remake music video “All Your Dream”, followed by a special fan party on March 24 & 25. The group made a music comeback with a release of a new music video “Kiss Me Like That” in August, followed with a new mini album “Heart”. They also met their fans through various fan events as well as appearances on variety shows. Shinhwa wrapped up their year-long anniversary celebration with a 2-day concert at Olympic Gymnastics Arena (KSPO Dome) on October 6 and 7, followed by a concert at Taipei Arena on October 13 and Hong Kong Asia World Expo Hall on November 24.

On January 1, 2019, it was announced that Eric has joined his bandmate Andy at TOP Media. To everyone’s surprise, Eric creates his own Youtube channel aguTV to share a various contents, from cooking, outings to how he failed to get a ticket for his own fan meeting. The following month, on February 16, he held a birthday fan meeting “2019 ERIC’s Moonday” at Kwanglim Art Center, BBCH Hall.

Eric was also expected to make a come back to drama this year. It was reported that Eric and Go Joon-hee are in talk to join KBS’s fantasy rom-com drama “Perfume” but he declined the offer. On Nov.05th, Eric was confirmed as lead actor for Channel A’s drama, “Yoobyeolna! Chef Moon” with Go Won-hee as lead actress. The drama is expected to be broadcast in March 2020.

On April 1, 2020, it was reported that Eric and Yoo In-na are reviewing offers to star in MBC’s rom-com drama ‘The Spy Who Loved Me’. About 2 months later, on June 22, Eric was confirmed as lead actor for MBC’s rom-com drama ‘The Spy Who Loved Me’ together with Yoo In-na and Lim Ju-hwan. The drama is scheduled to premiere sometime in October 2020.