"[29] On April 9, Tomorrow X Together announced their first overseas tour, a six-show debut showcase in six American cities—New York City, Chicago, Los Angeles, Dallas, Orlando, and Atlanta—over the course of two weeks, from May 9 to 24.

[31] Following their showcase in May, the vand performed at the 2019 iHeartRadio Wango Tango music concert at Dignity Health Sports Park in Los Angeles on June 1.

[34] On July 6, the band performed at the KCON 2019 NY music festival at Madison Square Garden, New York, in front of 55,000 spectators.

[37] On August 20, Big Hit Entertainment revealed members Taehyun and HueningKai had also been diagnosed with conjunctivitis, thus pushing the release date for the new album back from September to October.

[38] On October 21, 2019, Tomorrow X Tigether released their first studio album, The Dream Chapter: Magic, with "9 and Three Quarters (Run Away)" as lead single.

A total of four tracks from the album entered the Billboard World Digital Songs chart, with the lead single debuting at number two.

[51] On January 19, the band's Japanese television debut was announced with their first appearance on TV Asahi's Music Station.

[53] On April 28, Big Hit Entertainment set the release date of the band's second EP, The Dream Chapter: Eternity, for May 18, to be led by the single "Can't You See Me?".

[62] "Everlasting Shine" served as the twelfth opening theme of the anime Black Clover, which began airing on September 1.

[71] TXT released an original soundtrack titled "Your Light" for the JTBC teen-drama Live On on November 24, and member Yeonjun also made a cameo in the last episode.

[74] The album included the original Japanese song "Force", which served as the opening theme for the second season of anime World Trigger.

[79] The band released their second studio album, The Chaos Chapter: Freeze on May 31 with lead single "0X1=Lovesong (I Know I Love You)", featuring Seori.

The concert ran for 150 minutes, featured 25 songs, and was streamed through online platform VenewLive[89] to fans in 126 countries.

[94] The band also featured on the cover of Euphoria magazine, where they spoke to Aedan Juvet about being named the "it group" of K-pop's fourth generation.

[96][97] On March 14, it was announced that Yeonjun would be the new MC of SBS's Inkigayo alongside Roh Jeong-eui and Seo Bum-june.

[98][99] Tomorrow X Together released their fourth EP, Minisode 2: Thursday's Child, and its lead single "Good Boy Gone Bad" on May 9.

[102] On July 22, the group released an English single "Valley of Lies" featuring Puerto Rican rapper Iann Dior.

[111] The album included the original Japanese song "Ajisai no yōna koi (Hydrangea Love)" which served as the opening theme for the drama Saiko No Seito: Yomei Ichinen No Last Dance.

[114] On September 15, the band released the single "Back For More" with Anitta, and the song was performed for the first time at the MTV Video Music Awards.

[120] In July 2024, the music-themed Grammy Museum in Los Angeles, California announced that a special K-pop exhibit will take place in August 2024, displaying the accessories and performance gear worn by artists under Hybe, including Tomorrow X Together.

[122] On December 10, it was announced that the group would go on a long-term break after the 39th Golden Disc Awards on January 5, 2025, to spend time with their families and rest, but with plans to return later in the year.

[126] According to Rolling Stone, Tomorrow X Together's music "dabbles in disco, shoegaze, indie rock, and pop" and discusses "personal stories about the growing pains that come along with being a teenager".

[128] NME described the group's discography as mostly "bright, breezy and blissfully free from life's worries" and "focusing more on fantasy and fun".

[130][131] In December 2019, the band was announced as exclusive models for Korean student uniform brand Skoolooks' 2020 collections.

[132] In February 2021, Tomorrow X Together was selected as "main characters" in TikTok's #BeMyValentine global campaign to celebrate Valentine's Day.

[134] In July 2021, the band was revealed to be the newest brand ambassadors of Philippine telecommunications giant Smart Communications for its "Build Your Own Giga" campaign.

[136] In May 2022, the band was announced as the global ambassadors for Korean skin care brand Ma:nyo factory.