The song comes off their new album, out May 6, called "Save Roll and Rock."
Their last full-length release was 2008's "Folie à Deux."
Since their hiatus, each member went on to various side projects, including Pete Wentz's dubstep project Black Cards.
Guitarist Joe Trohman and Andy Hurley have been playing in metalcore supergroup The Damned Things.
And Patrick Stump released a solo album, "Soul Punk," which was widely regarded as a commercial failure.
Stump released an incredibly emotional blog post about the failure of "Soul Punk" last February.
The post has since been deleted, but it dealt with Stump's disappointment in his ability to find musical success after the early fame of Fall Out Boy:
"I hate feeling like the awkward adult husk of a discarded once-cute child actor... I'm debating going back to school and learning a proper trade. It's tempting to say I won't ever play/tour/record again, but I think that's probably just pent up poor-me emotional pessimism talking (I suppose can be excused of that though right? I am the guy from That Emo Band after all)."