The band consists of Jung Yong-hwa (leader, main vocals, guitar, keyboard, rap), Kang Min-hyuk (drums), and Lee Jung-shin (bass).

First bassist Kwon Kwang-jin left the band after they released their debut Japanese extended play Now or Never in 2009, and was replaced by Lee Jung-shin.

CN is an initialism for Code Name, while BLUE is a backronym for burning, lovely, untouchable, and emotional; it is meant to portray the images of Jong-hyun, Min-hyuk, Jung-shin, and Yong-hwa, respectively.

In late September, their original bassist Kwon Kwang-jin left the band and was replaced by Lee Jung-shin later that year.

It was promoted with the track "Love", which peaked at number two on Gaon, matching the success the band found earlier with "I'm a Loner".

The song reached number eight on the Oricon Daily Chart, marking the first time the band made it inside the top 10.

[14] The same year, Kang Min-hyuk and Lee Jong-hyun made their acting debut in the omnibus film Acoustic.

They then kick start their 2011 Japanese promotions with a Zepp Tour in four cities – Osaka, Fukuoka, Nagoya and Tokyo – from January 9 to 16.

Countdown and KBS Music Bank, thus marking the first time the band won "triple crown" on the shows.

[20] In April, it was announced that Jung Yong-hwa and Kang Min-hyuk were cast in the MBC drama Heartstrings, which started airing on June 29.

In November, "In My Head" claimed a gold record accreditation according to the RIAJ, meaning that the album sold over 100,000 copies within a month of going on sale.

The band wrapped up promotion with 4 music show award wins on April 22 with a goodbye performance on SBS' Inkigayo.

On January 14, which is CNBLUE's third anniversary, the band's fourth EP Re:Blue and music video of the lead single "I'm Sorry" were released.

[60] CNBLUE had also participated in the annual two-day Japanese rock festival Summer Sonic 2013 as one of the line-ups[61] along with their labelmate F.T.

On November 26, CNBLUE released their first ever "best-of" album in Korea, titled Present with the Korean version of the band's Japanese songs.

[69] The band then embarked on the CNBLUE 2014 Arena Tour: Wave from October to November in Aichi, Tokyo, Osaka, Miyagi, and Fukuoka.

[70] On December 6, CNBLUE was the only Korean artist to participate at the 2015 iQiyi All-Star Carnival in Beijing, China, where they received the "Best Asia Group" award.

They were the highest ranked Korean artist (followed by Girls' Generation's "Mr. Mr" at number 18 and Infinite's "Last Romeo" at number 48) on a list of "Twitter's 50 Most-Tweeted Songs of 2014" which included worldwide artists like John Legend, Ariana Grande, Beyonce, Pharrell Williams, Lady GaGa, Enrique Iglesias, Maroon 5, Coldplay and One Direction[72][73][74] Billboard K-Town included the EP on their list of the "10 Best K-Pop Albums of 2014" at #9, calling the tracks "Can't Stop" and "Like a Child" "some of the most accessible Korean rock tunes to come out of the scene this year," and "Cold Love" a "gritty ballad" and "Diamond Girl" a feisty rock jam.

[76] After an absence of domestic band promotions in one year and seven months in, CNBLUE released their second studio album 2gether and lead single "Cinderella" on September 14.

[78][79] The single peaked at number 10 on the Gaon Digital Chart,[80] ultimately earning the band five music show wins.

Jung Hae-wook of News Tomato complimented the band on the mixture of electronic rock and being able to form a distinct sound between the tracks, as well as their effort to experiment in order to establish its musical identity.

Jeff Benjamin of Billboard stated that in spite of the change in direction of the band's music on the album, their "sentimental songwriting" and "vivacious energy" persisted.

[103] On August 28, 2019, Jonghyun announced he was leaving CNBLUE due to his connections with the Burning Sun scandal and backlash over inappropriate messages towards a YouTuber.

[104][105] On October 20, 2020, it was announced that the 3 remaining members of CNBLUE had successfully renewed their contracts and are releasing their eighth mini album, Re-Code and its lead single "Then, Now and Forever", on November 17.

[106][107][108] CNBLUE launched a reality-variety show, Secret Tour: Don't Call My Name to celebrate their 10th debut anniversary.

[112] On August 5, CNBLUE announced a new Asia tour titled 'VOYAGE into X,' which was scheduled to be held in five countries: South Korea, China (Macau), Taiwan, Thailand, Malaysia, and Hong Kong.

[113] CNBLUE and its agency FNC Entertainment were sued by Korean punk band Crying Nut for unauthorized use of their song "Pilsal Off-Side" on Mnet's "M Countdown" in 2010.

[115] Crying Nut allegedly posted online that CNBLUE "must pay the penalties for intellectual property rights infringement".

[114] CNBLUE later countersued Crying Nut for allegedly accusing CNBLUE of copyright infringement, filing an injunction against Crying Nut's online criticisms,[116] claiming that the intellectual property theft was the responsibility of CJ E&M and the unspecified company responsible for the DVD sales.

[119] In July 2021, CNBLUE participated in a summer donation campaign by Happy Bean through the non-profit foundation, LOVE FNC.