Bettencourt has recorded a solo album and has founded rock bands including Mourning Widows, DramaGods, and Satellite Party.

[3] After playing in the Boston-based hair metal act Sinful,[4] Bettencourt rose to fame as a guitarist for the Boston-area group Extreme,[5][6] which he joined in 1985.

In 1995, Extreme released the album Waiting for the Punchline, but the band broke up in 1996 when Bettencourt decided to pursue a solo career.

[3] In 2007, Extreme reformed with its original lineup (with the exception of Paul Geary) to begin work on a new album, Saudades de Rock.

[15] Bettencourt provided rhythm guitar on the single version of Janet Jackson's "Black Cat" (1990)[16] which became a number one hit on the Billboard Hot 100.

[3] On December 16, 1997, Bettencourt's new band Mourning Widows (whose name was inspired by writing he had seen on a church wall in Portugal) released their self-titled debut album in Japan on Polydor Records.

In 2006, DramaGods contributed their song "S'OK" to the album project Artists for Charity—Guitarists 4 the Kids, produced by Slang Productions to assist World Vision Canada in helping children in need.

Bettencourt was the lead guitarist for Satellite Party, which is a band formed by Jane's Addiction frontman Perry Farrell.

Bettencourt helped produce Ultra Payloaded, the debut album by Satellite Party released on May 29, 2007, on Columbia Records.

The following year, Bettencourt was featured in a song and video called "Best Night Ever"[19] by Marshall Eriksen, a character on How I Met Your Mother.

[22] On February 12, 2023, Bettencourt performed at the Super Bowl LVII halftime show as part of Rihanna's backing band.

Bettencourt's long term girlfriend is dancer Christina Chandler, although there have been unsubstantiated rumors in September 2024 that they may have recently married privately.

[24][25] with Extreme as Nuno with Mourning Widows with Population 1 with DramaGods with Satellite Party with Generation Axe Solo career as a guest musician