The band members met during freshman orientation at Tufts University in 1991. A year later, after writing a few songs in their dorm rooms, the band named themselves "Gus" and booked their first gig. The band independently recorded their first album in 1994, entitled Parachute, while still in college. Shortly after the release of Parachute another artist called Gus signed a deal with a major record company, forcing the band to rename themselves "Guster." In 1996, the band independently recorded and released their second album, Goldfly. In 1998 the band signed to Sire Records and re-released Goldfly. A year later, the band released the album Lost and Gone Forever, produced by Steve Lillywhite. With the backing of a major label, the band appeared on late night shows like David Letterman. The band also released their first video, a song from L&GF entitled Fa Fa. The band released their fourth album, Keep it Together in 2003, with the first single, Amsterdam, getting significant play on the radio.
The characteristic usually first brought up about the band is their choice of instruments: two members playing acoustic guitars, and one member playing congos. While Guster's studio albums include more instruments (e.g. violin, bass, drum kit), their live shows generally kept this line up until the Keep it Together tour. The complexity of the new album required the addition of Joe Pisapia (guitar, keyboards, backup vocals), as well as allowed the original members to diversify their instrument choice (e.g. Ryan playing bass, Brian playing drum kit). Guster's sound is also defined by their vocal harmonies, with both Ryan and Adam singing lead vocals on different songs.
The band is also known for their connection with their fans. The band regularly updates a road journal on their website, and can often be found after shows for autographs.