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 of high school 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 he 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 2005, Mun graduated from Dongguk University with a major in Theater and Film.
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).
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. However the stunt car driver misunderstood the signals drove at them at 40 km/h and did not stop in front of them as planned.
In August, after the successful run of Super Rookie, especially in Japan, Mun collaborated again with its writers in Invincible Parachute Agent (also known as Korea Secret Agency).
Shinhwa's 10th Anniversary concert in March 2008, that marked the start of Shinhwa's hiatus as a group to fulfill Korea mandatory military duty. 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.
Mun gave up his American citizenship in 2003, to be able to serve his military duty. 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 drama, Mun served non-active duty e.g. public service worker after undergoing four weeks of basic training. He was discharged on 30 October 2010.
After being discharged, Mun's first project was supposed to be KBS's 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 1 July 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 23 March 2012, launched the concerts 2012 Shinhwa Grand Tour: The Return throughout Asia and their first exclusive variety program Shinhwa Broadcast premiered on 17 March 2012 on cable channel JTBC.
Mun's rap is featured on Brown Eyed Girls' Ga In's digital single "Nostalgia", released on 30 November 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.
Mun along with Shinhwa won Mwave Global Star Awards as well as many music shows awards and a Triple Crown on M Countdown for their music comeback.
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.
Despite its average 7% Nielsen rating, Mun and the team of Discovery of Romance drama received praise for their acting and Eric 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 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 Taeha Discovery of Romance stays in top 10 at #6.
Mun released Shinhwa's 12th studio album "WE" in 2015. Shinhwa broke their previous record with 10 wins (a Triple Crown at Mnet's M! Countdown) for this album. Mun and Shinhwa were on concert tour starting in May 2015 and ended with an Encore concert in Seoul in August. Shinhwa also performed at KCON LA for the first time in early August of that year.
After Shinhwa's 18 Anniversary in March, Eric returned to acting and appeared in the South Korean TV cable (tvN) drama Another Oh Hae-young with Seo Hyun-jin. The drama premiered on May 2 with better rating than its predecessor Pied Piper. It broke its projected rating of 5% of on its 6th episode and becomes tvN's all time highest rated drama for their Monday - Tuesday time-slot with the rating of 9.9% for its final episode. Another Oh Hae-young team was rewarded a trip to Thailand after the drama ended. At tvN10 Awards on October 9, Mun was awarded the title of "Ro-co King". Seo Hyun-jin was also crowned "Ro-co Queen" for their roles in Another Oh Hae-Young.
On September 16, in a preview for the new season of tvN "Three Meals a Day", it's shown Eric joined as a cast member for Season 3 of Three Meals A Day - Fishing Village 3 with Lee Seo-jin and Yoon Kyun-sang. This season of Fishing Village was filmed at Deukryang Island. The season premiere was on October 14. It was Eric's first appearance as a cast member of a variety show without Shinhwa. Eric surprised everyone with his great cooking skills that earned him the E-Chef title. The show had great rating of above 10% on average with the highest rating of 11.536% (AGB) 13% (TNmS).
At the end of November 2016, Eric and Shinhwa released a mini album 'Unchanging: Orange' as part 1 of their 13th album.
Eric was chosen to be the model for Jean Michael Basquiat a new premium golf wears and accessories by CJ E&M and ULOS, a Men's cosmetics & skincare by Ostuka Korea.
Shinhwa followed up with a comeback in January 2017 with 'Unchanging: Touch' as the 2nd 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+.
Continue to be Jean Michael Basquiat and ULOS brand representative, Eric was also chosen to be the representative for Bibigo by CJ E&M, a global Korean food brand CJ Cheil Jedang. Eric together with Kim Sangjoong and Kim Myungmin were chosen by Netmarble Game for their new CF, Lineage 2 Revolution, an online & mobile game. Netmmarble Game also released a web drama series featuring Kim Sangjoong, Kim Myung-min, and Eric Mun and for their big-scale mobile MMORPG 'Lineage2 Revolution'. In the web drama, Eric plays a rookie employee that is trying to survive in the company while reigning as the King in 'Lineage2 Revolution'. However, it is revealed that Eric is an actual high level player in real life.
Eric started dating actress Park Si-yeon in 2004. The couple broke up in 2007. After dating speculation came out from several news sources on February 23, 2017, management from both sides confirmed that Eric is dating actress and model, Na Hye-mi. It is said that they have been dating for more than four years, since the dating rumour first appeared back in 2014. On April 17, 2017, through Shinhwa Company's Facebook, Eric announced that he and Hyemi are to get married on July 1, 2017 with a private wedding ceremony at a church with family and friends.