Prior to his association with the Bosstones, Barrett played in the local Boston area bands Cheapskates, Toxic Toast, and Impact Unit.

Barrett appeared on two Brain Failure tracks, which are featured on their split entitled Beijing to Boston with Big D and the Kids Table.

He also made guest appearances on tracks from No Use for a Name, Clowns for Progress, the Stubborn All-Stars, and local Boston band Darkbuster.

Barrett announced that the tenth official Hometown Throwdown would occur between December 26–30, 2007 at Cambridge, Massachusetts' famed Middle East after a five-year hiatus.

In January 2022, Rolling Stone reported that Barrett had produced a song and music video for Robert F. Kennedy, Jr. to promote an anti-vaccine rally.

Though the band did not state the reason for the breakup, Rolling Stone speculated that it was related to Barrett's involvement in the song and video.

[3] News of his involvement with Kennedy and the band's breakup came shortly after Barrett left Jimmy Kimmel Live!

[5] On March 6, 2023, it was announced that Barrett had formed a new band with members of the Offspring, Street Dogs, Smash Mouth and the Briggs called The Defiant.

Barrett portrays a prison inmate in the unreleased 1999 film Big Helium Dog.

Barrett has also done voice-over work for Minoriteam and appears in the documentary film American Hardcore.

He also portrayed rock pioneer Bill Haley in the miniseries Shake, Rattle, and Roll: An American Love Story.