The single prologue of EXO-K and EXO-M, "What Is Love" was released on January 30, 2012 in South Korea and mainland China. The single was positioned at number 88 on the Korean chart Gaon Single Chart. On March 9, the group released its second single prologue entitled «History», which was written and produced by Thomas Troelsen and Remee. The single was positioned at number 78 in Gaon Single Chart and number 6 on China's Sina Music Chart. A concert by the group took place at the Olympic Stadium in Seoul on March 31. Approximately 3,000 fans of 8,000 were selected to attend. A second concert was held in the great Hall of Beijing University of Economics and business, April 1. Both subunits released his third debut single entitled "Mama" April 8 followed by an EP of the same name the next day. The two subunits promoted the album separately in two countries. On April 8, one day before the release of the EP, EXO-K had their debut performance on the musical program of South Korea "Inkigayo", while EXO-M made its debut in China Awards 12th Yinyue Fengyun Bang Awards the same day. The Mandarin version of "Mama" headlined at the number 2 in the Chinese chart Sina.com, while the Korean version was positioned number 1 of Gaon Albums Chart and number 8 on the Billboard World Albums Chart. The Mandarin version of the music video "Mama" reached number 1 on the websites of Chinese transmission, while the Korean version was ranked number 7 on YouTube's Global Chart. At the end of April, EXO-M appeared as guests in the concert of Super Junior "Super Show 4" in Jakarta, Indonesia. In November 2012, EXO won an award as Best New Group of Asian Artists in 2012 Mnet Asian Music Awards. EXO-K three nominations in 27th Golden Disk Awards gaining in the newcomer category. EXO-M awarded the Most Popular Group in 2013 Top Chinese Music Awards.
The group released their first studio album entitled "XOXO" in June 2013 with two versions, Korean edition "Kiss" and the "Hug" mandarin. A difference to the era of "Mama", EXO-K and EXO-M did their promotions in separate, however, with "XOXO" had their promotions jointly; mainly in South Korea. EXO recorded the single main "Wolf" but the rest of the songs they recorded them separately. The two versions collectively ranked number 1 in Billboard World Albums Chart a week after its release.
The repackage album entitled "Growl", was released on August 5, 2013, with three additional new tracks. The single reissue, "Growl", was released on August 1, 2013. "Growl" achieved 10.554 points in "Inkigayo". "Growl" headlined at number 1 in the four most important music programs in Korea, winning a total of ten trophies in three consecutive weeks. The single was positioned at number 3 in Korea K-Pop Hot 100 of Billboard and number 2 in Gaon Chart. In December 2013, two versions of "XOXO", sold 1,000,000 copies, marking to EXO as the first Korean artist to sell a million copies in twelve years and broke the record for being sold faster K-pop act. "XOXO" was named the Album of the Year in 2013 Mnet Asian Music Awards, making EXO as the youngest boyband in the prize, won the 'Disk Daesang' award at several award ceremonies such as the Golden Disk Awards and Seoul Music Awards. The second EP of the band entitled "Miracles in December" was officially released on December 9, 2013 as a special album of winter through commercial outlets in South Korea and online music stores. EXO jumped to his album promotions through their reality show "EXO's Showtime", which premiered on November 28, 2013 in the cable MBC Every 1. Baekhyun, Chen and D.O. sing the single main of the album "Miracles in December", in "M! Countdown", December 5. Luhan also joined the trio on stage for the promotions of the first single on other music programs.
EXO ended 2013 with six annual albums in the Top 10 best-selling albums of Gaon, including all their releases of records, both in the Korean version in mandarin, as well as their first EP "Mama".
The third EP of the group "Overdose", was released on May 7, 2014. It was originally scheduled to be released on April 21, but was delayed by the Swreck of the Sewol on April 16. "Overdose" was promoted in the same way as "Mama", with EXO-K promoting EXO-M in China and South Korea. The album reached 660,000+ pre-orders before its release, so it is the most pre-ordered EP in history. The Korean edition was also positioned at number 2 in Billboard's World Albums Chart and number 129 on the "Billboard 200", making the male group of Korea with the highest Billboard 200 graphics to EXO. "Overdose" became the best-selling album in Sotuh Korea in 2014 and the first mini-album in finishing the annual graphics and winning the Album of the Year at Mnet Asian Music Awards. At the end of the year, EXO was the top-selling K-pop artist in Japan. On May 15, 2015, S.M. Entertainment confirmed that the EXO-M, Kris, leader signed a lawsuit against the agency, indicating violation of human rights as the main reason. On October 10 Luhan also signed a lawsuit against S.M. Entertainment, due to health problems and be treated differently than the Korean members. S.M. Entertainment announced that the group will continue promoting with ten members. The group held their first tour "EXO From. EXOPLANET #1 - THE LOST PLANET", beginning on may 24 in the Olympic Stadium of Seoul. Tickets of the concert is finished 1.47 seconds.
The second tour of EXO was announced in January 2015, titled The EXO'luXion. Five concerts were held in Seoul in the Olympic Stadium, from March 7. One million fans had tried to buy tickets online. On February 4, 2015, S.M. Entertainment, signed a lawsuit against Kris and Luhan by illegally continue their promotions in China. The demand was to stop their actions and the advertisement in the use of the trademark S.M.
The second album by EXO, Exodus, was released March 30 in Mandarin and Korean versions. Domestic sales for the album exceeded 500,000 within 24 hours, setting a new sales record. The main single, "Call Me Baby", was released on March 27 due to leaked versions of the song. The music video was released four days later, the Korean version received more than 4,000,000 view and the Mandarin version 2,000,000 views in just 24 hours. EXO starred in the mini-drama entitled "EXO Next Door" with Moon Ga-young actress.
"Call Me Baby", proved to be successful winning eighteen times in musical programs of South Korea, making it the second most awarded song ever. "EXODUS (Korean version) " also broke records after remaining number one in Gaon Album Chart for four consecutive weeks. The album eventually came to sell more than one million copies, and is the second album of the group after "XOXO" to do so. "EXODUS" was named as 'Album of the year' in the 2015 Mnet Asian Music Awards, making this the third consecutive victory for the group from 2013.
On April 22, the father of Tao issued a letter through Weibo expressing his feelings for his son to leave the group and return to China; due to the lack of support with regard to the developments of individual career and health problems. Tao had suffered previously several injuries, including a tendon torn in ankle, that they had not properly been treated more worsened, and had to leave for promotions for the second album by the group "EXODUS". On April 23, S.M. Entertainment released an official statement saying that they were going to be looking for a solution in the sense of development through negotiation with Tao and his father. Tao later confirmed that had left S.M. Entertainment and after failed negotiations, Tao presented a formal complaint against S.M. Entertainment on August 24 for the termination of his contract.