Wentz was primarily involved in the Chicago hardcore punk scene and was in several bands in the late 1990s. These included First Born, Extinction, Arma Angelus (alongside Tim McIlrath, frontman of Rise Against), Yellow Road Priest, and Racetraitor. He and Arma Angelus' bassist Joe Trohman founded the pop-punk band Fall Out Boy after Trohman introduced Pete to a musical acquaintance, Patrick Stump. Andy Hurley agreed to drum part-time, but only joined the band full-time later. In 2004, Arma Angelus, the band in which Wentz was the vocalist/screamer, played its last show.

In 2002, Fall Out Boy released an EP called Fall Out Boy/Project Rocket Split EP. Soon after, in 2003, the band released Fall Out Boy's Evening Out with Your Girlfriend on Uprising Records. This album would later be digitally remastered and reissued after the band's second, more successful full-album release Take This To Your Grave on the independent label Fueled by Ramen Records. Later in 2003, Wentz and the r