After moving to Los Angeles to make their third album, they added a fast punk beat, changed the lyrics, and altered the chords of the chorus.

The recording process was "very complex" due to the many layers in the song, but "fun", according to guitarist Ray Toro, who extolled the end result:[11] "My two favorite tracks are 'Welcome to the Black Parade' and 'Famous Last Words'.

It features the Patient (the main character of the album, played by Lukas Haas) dressed in a hospital gown, and being taken by death in the form of a "Black Parade".

[13] The setting of the music video transitions from a hospital room to a surreal cityscape with ash-covered wreckage, snow, black confetti, and destroyed buildings.

[14] Tom Breihan of the Village Voice regarded the video as "revealing a new stage of [My Chemical Romance's] persona".

[21] David Fricke from Rolling Stone praised Way's "full rock-hero tilt" singing of the vocal hook ("We'll carry on.").

In addition, it topped Modern Rock Tracks for seven weeks in a row, and is the band's only number one on this chart to date.

In the UK, the single knocked Razorlight's "America" off the number one spot on October 15, 2006, after extensive airplay.

[25] The solo piano intro of the song, which opens on a single G5 note held for the duration of a half note, has become iconic due to the song's popularity, especially among fans of My Chemical Romance and the wider genre, where it is seen as an inside joke and nostalgic of the mid-2000s emo subculture.

Andrew Lloyd Webber, for example, asked his Twitter followers what they thought when listening to the note, as a reference to the song.

In July 2023, in the wake of comments perceived as anti-LGBTQ by Florida governor and presidential candidate Ron DeSantis, the band Sub-Radio released a viral parody of the song called Welcome to the Pride Parade, replacing the lyric "We'll carry on" with "You're scaring Ron.