Visual artist Gerard Way formed MCR in 2001 as an artistic response to 9/11. He recruited his younger brother Mikey to play bass as well as guitarist Ray Toro and drummer Matt Pelissier. Rhythm guitarist Frank Iero joined the following year after his band, Pencey Prep, broke up.
The band built itself up from scratch, building an audience at New Jersey basement parties, before breaking out with their second album, 2004's Three Cheers For Sweet Revenge
and the hit single "I'm Not Okay (I Promise)
MCR had an international hit with their 2006 concept album The Black Parade, which centered on a dying character with cancer known as "The Patient". Musically, it incorporated Broadway theatrics and Glam Rock.
Original drummer Matt Pelissier left MCR after Three Cheers for Sweet Revenge, making way for Bob Bryar on The Black Parade, but he left in 2010. Michael Pedicone joined the band as a touring drummer later that year, but he was sacked in 2011 after the band accused him of stealing from them. He later admitted to making a "tremendous mistake."
Their fourth album, Danger Days: The True Lives Of The Fabulous Killjoys, was inspired by the Way brothers' love of comics books and sci-fi.
Gerard Way married Mindless Self Indulgence bass player LynZ on September 3, 2007 after the final date of Linkin Park's Projekt Revolution tour in Colorado. The low key ceremony was performed backstage with the help of a member of Live Nation's touring staff who was also an ordained minister. In 2009, they welcomed a daughter, Bandit Lee Way.
It was Mikey Way who suggested the band's name. Whilst working in a Barnes & Noble, he was struck by the title of a book by Irvine Welsh named Ecstasy: Three Tales of Chemical Romance.
Gerard Way struggled with alcoholism and prescription drug addiction for many years, but got sober in August 2004.
MCR broke the news to fans on March 22, 2013 that they had broken up. No reason was given for the split, but a few days later, Gerard Way cited at a show at New Jersey's Bamboozle festival on Saturday May 19, 2012 as being a moment when his perspective shifted. He said he was uncharacteristically nervous and anxious, and in the aftermath, "I hollowed out, stopped listening to music, never picked up a pencil, started slipping into old habits."
In 2014, Gerard told NME he broke up the band to save himself after a particularly frightening relapse into alcoholism following the release of MCR's final album. "I relapsed, not into drugs but booze," he explained. "I was self-medicating again to get through, and I'd forgotten how miserable that made me. It took me to the dark place again, but there was more at stake this time. I started to face the hypothetical reality of Bandit not having a father. I started taking that seriously, thinking, 'I want her to have a dad. A guy that's present. Because one way or another – either by death or by asylum, she's gonna be fatherless if I keep this up.'"
The band announced a reunion show on October 31, 2019, which took place on December 20, 2019 at the Shrine Expo Hall in Los Angeles. They kicked off their first gig in seven years with "I'm Not Okay (I Promise)