Killswitch Engage formed following the dissolution of two other metalcore bands, those being: Overcast and Aftershock in 1999. After Overcast broke up in 1998, bassist Mike D'Antonio attended jam sessions with Aftershock guitarist Adam Dutkiewicz. Dutkiewicz then switched to drums and recruited guitarist Joel Stroetzel from Aftershock and vocalist Jesse Leach of Nothing Stays Gold (who were signed to Dutkiewicz's brother Tobias' record label and also the vocalist of Aftershock) to form the new band, Killswitch Engage, a name derived from an episode of the television series The X-Files entitled "Kill Switch", written by William Gibson, who, in turn, so named that episode after meeting the industrial band Kill Switch...Klick.
In 1999, the band recorded a four track demo that included the track Soilborn; the demo was released at the band's first show, opening for In Flames.
Their self-titled debut album came in the following year. That album attracted the interest of Carl Severson, who worked at 'Roadrunner Records' and soon later signed them.
For a brief time in 2000 and 2001, ex-Overcast guitarist Pete Cortese joined Killswitch Engage, but soon left when he became a father.
Alive or Just Breathing (2001), so named for the lyrics in the song Just Barely Breathing, arrived as their sophomore effort.
Dutkiewicz then moved to guitar and former Aftershock drummer Tom Gomes filled in the vacant position. After Leach was married in April, 2002 then began touring again, he suddenly fell into depression and left the band a few days before a show; the resignation was sent by e-mail. A replacement was found in the form of Howard Jones (ex-Blood Has Been Shed). In 2003 the first song to feature Jones, When Darkness Falls, appeared on the soundtrack of the 2003 horror film Freddy vs. Jason.
The End of Heartache (2004) peaked at 21 on the Billboard 200 with 38,000 sales in its first week, it also peaked at 39 on the Australian Albums Chart. The album went on to sell more than 500,000 copies in the US and was certified gold on December 7, 2007. The title track appeared on the movie Resident Evil: Apocalypse soundtrack and was nominated for Best Metal Performance for the 47th Grammy Awards in 2005. In late 2004, the album was re-released as a special edition, with a second disc featuring various live performances, a Japanese bonus track and a re-recorded version of the track Irreversal.
The band then played the Reading and Leeds Festivals in August 2006, having already played Australian dates without Dutkiewicz, who was suffering from back problems and needed corrective surgery.
Recorded in three months and Mixed by Dutkiewicz, As Daylight Dies was released on November 21, 2006 to peak at 32 on the Billboard 200 chart with 60,000 sales in its first week; the album proved to be one of their biggest albums. The album's first single, My Curse, peaked at 21 on the Hot Mainstream Rock Tracks chart, and was featured in the video games Sleeping Dogs, Guitar Hero III: Legends of Rock, Burnout Dominator and Burnout Paradise.
Dutkiewicz's back problems continued to plague him in early 2007 and he was temporarely replaced by frontman Patrick Lachman (of Damageplan and The Mercy Clinic) during the No Fear Tour; Dutkiewicz returned in time to finish the tour.
2009 saw the band release a second self-titled album [yes - a second!] that debuted at 7 on the Billboard 200, marking the band's highest chart position for an album. During July and August, the band took part in the Mayhem Festival with headliners Marilyn Manson, Slayer and Bullet for My Valentine. In February 2010, vocalist Howard Jones would not be performing with the band during their winter tour with The Devil Wears Prada and Dark Tranquillity; All That Remains vocalist Philip Labonte would temporarily replace him.
D'Antonio started the hardcore band Death Ray Vision, with Shadows Fall vocalist Brian Fair and ex-Killswitch Engage guitarist Pete Cortese.
January 2012, Howard Jones left; Jesse Leach would return to fill the void.
The next album, Disarm the Descent (2013), debuted at 15 in the UK charts and 7 on the Billboard top 200. In December 2013 the track In Due Time was nominated for "Best Metal Performance" at the 2014 Grammy Awards, but ended off loosing to God Is Dead? by Black Sabbath.
Incarnate. their 2016 effort, would follow.