Delirious? began life as a worship band for a youth outreach event called "Cutting Edge", instigated by the Arun Community Church in Littlehampton, West Sussex, England. As the popularity of these events increased, and the band also played at other "Cutting Edge" events along the South Coast reaching as far as Southampton. However the band remained as the house band for Cutting Edge for several years despite their soaring popularity, what originally began as an event in the school hall soon moved to the school's sports hall with the organisers having to charge £1 to control the numbers attending. In 1996 the show was taken outside with a show performed on the green next to Littlehampton's beach and the derelict Beach Hotel, an estimated 4000 people attended while Channel 4 filmed it for a documentary. The last ever Cutting Edge was held the following summer in 1997, again on the beach where the band played from their Cutting Edge back catalogue and the King of Fools album.

The music became well known in Christian circles, and demand grew for recordings. Four EPs were released under the "Cutting Edge" name before the group made the decision to turn professional and change their name to "Delirious?" in 1996. By that time, they had already sold over seventy thousand EPs by mail order.

Many of the band's most famous songs were written during this era, including "I Could Sing Of Your Love Forever", "The Happy Song", and "Lord, You Have My Heart".

On 30 August 1995, Martin, his wife, and Jon were involved in a near-fatal car accident. Jon and Martin's wife were unhurt but Martin was hospitalized for several weeks. While in the hospital, Martin made the decision to become a full-time musician, and Delirious? was conceptually born. They gained success in 1997 following the release of King of Fools, the first studio album released under their new name. King of Fools eventually went 'Silver' in the United Kingdom, and Delirious? became one of the most popular and well-known Christian rock groups both in the UK and the United States. Songs such as "Deeper" and "History Maker" gained anthemic status and still surface regularly at Christian youth events. Delirious? also released three singles to the mainstream UK Charts - "White Ribbon Day", "Deeper", and "Promise". The last two both reached number twenty with very little radio airplay; "Deeper" remains the band's best-selling single with over thirty thousand copies sold. The group signed to EMI for its British releases but in 1997 the group signed to both Virgin and Sparrow Records for distribution in secular and Christian markets in the United States. The success of the King of Fools album allowed the band to tour the UK for the first time comprehensively, with venues such as Leeds Town & Country Club and Brixton Academy taken in. Delirious chose to tour without a support band, instead using a DJ and a large visual aspect to the performance.

During the summer of 1997, Stewart Smith and his wife lost their unborn baby through a miscarriage, inspiring the song "Summer of Love" on the DeEPer EP, a re-release of the "Deeper" single. The re-release attained number thirty-nine on the UK Charts.

In 1998, the band released their second live album, d:tour, which featured many of the songs from the King Of Fools album in addition to some songs from the Cutting Edge period. It was recorded at Southampton Guildhall.

The 1999 album Mezzamorphis attained number twenty-five in the album charts (number two in the independent section), and soon became certified silver in the UK. The band found resistance in the mainstream due to their "Christian" label despite generally positive reviews in the music press. However, the work was aimed as a "secular" audience, causing many former fans to shun the album and claiming that Delirious? had "sold out" to mainstream markets. The Virgin marketed version omitted three songs, "Jesus' Blood", which was explicitly faith oriented, and the praise and worship songs "Love Falls Down" and "Kiss Your Feet".

Singles from Mezzamorphis gained some British chart success. For example, the first single, "See The Star", peaked at number sixteen on the charts, following an appearance on television show The Big Breakfast. The second single, "It's OK", reached number eighteen. In the US, "Gravity" was chosen over "See the Star" as lead radio single for promotion.

In 2000, the band released a worship-oriented album, Glo (short for glorious). This album was the number one Christian seller for eight months. Several songs from the album, while not being released as actual singles, gained immense popularity in the Christian-music world, most notably the guitar-driven "My Glorious" and the more introspective "Jesus' Blood". The track "Investigate" eventually became a favourite concert closer for Delirious?. That year the band toured the US and appeared to an audience of 55,000 at the Creation Festival.

The second attempted mainstream album, Audio Lessonover? (an anagram of 'Radio One Loves Us') was released in 2001. The single "Waiting For The Summer" did manage to reach number twenty-six on the charts. The album was later released as Touch in North America with some significant edits. That year the group toured with Bon Jovi and Matchbox Twenty. Again they received criticism for "selling out" to achieve success in mainstream markets.

Deeper was released in early 2002. It is a double album comprising of many remastered classic worship songs from the Cutting Edge albums and previous work such as Glo and King Of Fools. It also includes some new versions and a new song, Not Forgotten.

Libertad was released in late 2002. A new studio album, but made specifically for the band's growing Spanish audience. It comprises 12 classic Delirious? songs from the cutting edge days, all translated into Spanish and re-recorded. Even today, Martin Smith will occasionally sing stanzas of his songs in Spanish as can be heard on the live albums Access:d and Now Is The Time, and on Disc II of Touch.

In 2003, Delirious? released World Service, the first of what guitarist Stu G later described as 'a trilogy'. Although this was more of a worship-oriented album as was Glo, Delirious? released two singles to the German market: "Inside Outside" and "Every Little Thing". The former sold over twelve thousand copies, was number one in German radio station SWR3's chart, and spent seven weeks in the German singles charts peaking at number seventy-two. Delirious? also released two free MP3 downloads on mp3.com, both topping the Guitar Rock charts (the first for a full month). The first MP3, "Majesty (Here I Am)", hit number fifteen on the worldwide charts; the second, "Rain Down", reached number twenty-eight. The two together had amassed over 500,000 listens/downloads after fifty days. Delirious?’s World Service is finding success in the United Kingdom and America as well. The band’s American single "Rain Down" has become its biggest multi-format hit since "Deeper".

The band's sixth studio album, The Mission Bell was released in the UK in 2005. The album received very positive reviews, with Christianity Today, Jesus Freak Hideout, and Cross Rhythms all praising The Mission Bell for "Effectively stretching the boundaries of worship music". "Paint The Town Red" was released as a CD and iTunes single in the UK, entering the charts at number fifty-six. Several singles were released to CrossRhythms radio in the UK, all charting at number one for several weeks. The Mission Bell was nominated for the May 2007 Dove Awards, in the Rock/Contemporary Album of the Year Category, although it didn't win (Jars of Clay's Good Monsters won).

Delirious? spent much of 2007 recording and working on their new album Kingdom of Comfort with producer Sam Gibson. On the November 2, 2007, Delirious? announced their upcoming album which was then released in the US on April 1, 2008, and was to be released in the UK on April 14. This strategically coincided with the launch of the third version of their official site. The band made one of the tracks, "God Is Smiling", available as a free download in the members only section of the site called "The Living Room." The song is what the band call the "Living Room" version so a re-mixed version may be expected on the upcoming album. Another track, "We Give You Praise," has since been added as a free download.

When Stew Smith left the band at the end of April 2008, Paul Evans was drafted in to replace him as the bands drummer. Before leaving, Stew mentioned that a live album and DVD had been recorded whilst on tour in Brazil, as a collaboration project with André Valadão. This was titled Unidos, and has since become available in several countries, although no announcement has yet been made on a possible UK release date. On the 6th of July of the same year, the band announced via a press release that they would be "taking a break" at the end of 2009 to allow the band to focus on things close to them. Martin said that he wanted more time to spend with his family and devote more time to the Compassion Art project. On the 19th of September, it was announced that another live album and DVD would be recorded in Columbia as the band's final project before their split. The band also announced that they would release a final single to the UK charts in November, Love Will Find A Way, which was featured on Kingdom Of Comfort.