[2][3][4] His success as a singer, actor and host has earned him the title of "Triple Threat" entertainer and has established him as a top Hallyu star.

[8] Lee was first included in Forbes Korea Power Celebrity 40 list in 2010 placing seventh,[9] subsequently ranking fourth in 2011[10] and sixth in 2012, 2015 and 2022.

He then continued his studies obtaining two master's degrees, Marketing, Trade Theory as well as Finance and Cultural Contents at Dongguk Graduate School.

"Because You're My Girl", his debut song from his first album The Dream of a Moth, became a popular ballad which created a 'liking older women' syndrome in South Korea.

In 2007, he also won the Best Male Solo Artist award at the M.net KM Music Festival with his song "White Lie" from his third album Story of Separation.

[27] This was followed by the release of his fifth album, Tonight in 2011, a departure from his usual traditional ballads and encompasses more of a rock band-style sound and melodies.

[37] The title song "Return" set a record for being number one for six consecutive weeks on Billboard's Korea K-Pop Hot 100.

[51] This was followed by SBS's fantasy drama My Girlfriend Is a Nine-Tailed Fox in 2010, playing a university student who (despite strong discouragement from his grandfather) wants to drop out in order to pursue his dream of becoming an action movie star.

[61][62] In July 2015, Lee was cast in the period comedy film The Princess and the Matchmaker with Shim Eun-kyung, directed by The Face Reader director Han Jae-rim.

[71] Lee was a permanent cast member of the first season of 1 Night 2 Days, a segment of KBS's weekend variety show Happy Sunday, from November 2007 to February 2012.

[74] In October 2009, Lee took on a hosting role in SBS's Tuesday night talk show Strong Heart with Kang Ho-dong.

[78] Lee reunited with 1 Night 2 Days cast members and PD Na Young-seok in the travel-reality show New Journey to the West in 2015.

[84] In 2019, he joined the cast of Little Forest – a healing variety program designed as a home kids garden development project for children.

On July 24, Lee joined the reality program Loud as an MC and Special Agent, a unique position whose task is to provide the remaining contestants with warmth, guidance, and support as they prepare for the finale.

[90] In the same year, he won the Baeksang Arts Award for Best Male Variety Performer for his work in Busted!, Twogether, Hometown Flex, Sing Again and Master in the House.

[91] In 2022, Lee hosted SBS new year special program Circle House – a 10-episode healing talk show that candidly shares the real concerns of the MZ generation in Korea and seeks solutions with applicants.

[98][99] Lee's success as a singer, actor and host also earned him the titles "Triple Threat" entertainer, Emperor, and Prince of Ballad.

[111] In a survey conducted by DC Inside that was held for seven days in January 2023, Lee was voted the leading star who does good deeds with sincerity and not for keeping up an image.

[112] On February 1, 2016, Lee began his 21-month mandatory military service as an active duty soldier, entering Nonsan Army Recruit Training Center in South Chungcheong Province.

Other optional trainings include Krav Maga level 1 and long distance march of 400 kilometers (about 250 miles), where he was in the top 10% of the 1000 marathoners,[119] as part of the 'Black Panther' Brigade (which was re-designated as a decapitation unit named 13th Special Mission Brigade on December 1, 2017, with the mission of assassinating North Korean leaders in the event a war broke out within the two nations).

Later, on November 21, through an independent report by Dispatch, it was revealed that Lee had not been properly settled for 18 years of music revenue and was even gaslighted by his agency since debut.

[128] On November 25, 2022, Hook Entertainment claimed that the debt relationship with Lee has been settled in 2021 when their contract was renewed and the unsettled music revenue is false.

As a result, Lee's legal side has obtained evidence to sue Hook Entertainment for violation of management duties, and thus, the artist will be moving forward with the one-sided termination of his contract.

[133] Lee officially filed a criminal lawsuit against Hook Entertainment's CEO Kwon Jin-young, as well as its former and current directors on December 22, 2022.

[134] On April 21, 2023, it has been reported that the Ministry of Culture, Sports & Tourism has passed the Lee Seung-gi Incident Prevention Act.

The bill also prohibits agencies from forcing minor-aged celebrities to take excessive care of their appearance or making them work more than seven hours a day.

[138] In 2014, Lee collaborated with CJ E&M to provide assistance to an education contents donation event for low-income female students in the US.

[136] In 2020, to help with COVID-19 prevention and aid underprivileged children in Korea, Lee has donated ₩100 million to Good Neighbors, an international humanitarian and development NGO.

[143] For his 35th birthday on January 13, 2022, Lee became the first charity fairy under the entertainment category on the celebrity ranking service, CHOEAEDOL Celeb.

[145]In December 2022, Lee donated ₩2 billion in development funds to improve the medical environment of Seoul National University Children's Hospital.