Brian Bromberg was born on December 5, 1960, in Tucson, Arizona. His father, Howard Bromberg, was a working Tucson drummer and his brother David also played drums, so Bromberg started on drums and was playing professionally by thirteen. In school orchestra he played cello until the orchestra director, wanting someone on the unused double bass in the corner, steered him to it. From fourteen to eighteen he practiced for most of the day, took music classes at the University of Arizona while still in high school (lab band, orchestra and jazz combos), tested out of high school early, and then played five to seven nights a week in whatever bands would hire him.

His first break came in 1979, when the bassist Marc Johnson, then with Bill Evans, heard him in Tucson and later told Stan Getz, who needed a new bassist, about him. Bromberg auditioned and joined the Getz quintet in December 1979, just after turning nineteen, and spent nearly a year touring the world with the band. He then built a studio career in Los Angeles that took in film scores and singers: the soundtracks to The Fabulous Baker Boys (1989, with Dave Grusin) and Havana (1990), Anita O'Day's In a Mellow Tone (1989), Michel Legrand's Michel Plays Legrand (recorded September 1993), Lou Rawls's Rawls Sings Sinatra (2003), and four albums with Michael Bublé between 2003 and 2009.

His own records began with A New Day (BlackHawk, 1986) and Basses Loaded (Intima, 1988), and he moved quickly onto contemporary-jazz radio. Magic Rain (1989) was produced and arranged by Jeff Lorber and featured saxophonists Ernie Watts and Brandon Fields; BASSically Speaking (Nova, 1990) reworked his first album with new tracks and a guest spot by Freddie Hubbard, and reached number 7 on Billboard's contemporary jazz chart. He then made an acoustic date, It's About Time: The Acoustic Project, recorded live on May 21 and 22, 1991, with Hubbard, Watts, pianists Mike Garson and Mitchel Forman and his brother David on drums; it reached number 4 on the mainstream jazz chart. A self-titled electric album followed in 1993 on Nova, which folded the week it came out. His 1998 album You Know That Feeling, with trumpeter Rick Braun, pianist Joe Sample, Lorber and saxophonist Everette Harp, gave him his first number one on the smooth jazz airplay chart and stayed on the charts for seventeen consecutive months.

From 2001 he turned back toward acoustic jazz and, in parallel, toward tribute projects. Wood (recorded December 14 to 17, 2000, and issued in Japan in April 2001) was a trio date with pianist Randy Waldman and brother David that became a favorite of audiophile retailers; Wood II (2005 in Japan, 2006 in the United States) replaced the drummer with Vinnie Colaiuta. In between came Jaco (2002), a tribute to Jaco Pastorius that he recast around his own acoustic bass; Choices (2004); the JB Project with drummer Akira Jimbo and pianist Otmaro Ruiz, whose first album Brombo! appeared in March 2004; and Metal (2005), an instrumental rock set on which every guitar-sounding part is played on piccolo bass. Downright Upright, released in Japan in 2006 and in the United States in 2007 with George Duke, Lee Ritenour, Boney James, Kirk Whalum and Colaiuta, earned him a nomination for Best Contemporary Jazz Album at the 50th Annual Grammy Awards in February 2008; the award went to Herbie Hancock's River: The Joni Letters.

The next decade ran through Hands (2009), a solo double bass album recorded live in July 2008 and issued first in Japan; It Is What It Is (Artistry, August 2009), a funk-leaning electric bass record with a ten-piece horn section; Bromberg Plays Hendrix and In the Spirit of Jobim (both released in Japan before their 2012 American editions); and Compared to That (2012), a live-in-the-studio jazz date with horns, strings and a guest appearance by banjoist Béla Fleck. In 2011 he began a signature electric bass line with Carvin, which became Kiesel in 2015. Some years before 2016 he broke his back in a fall at home and spent a long rehabilitation relearning to carry the instruments; the record he made on recovering, Full Circle (2016), is an acoustic jazz album that opens and closes with tracks built on an old acetate of his late father's band, with Bromberg overdubbing bass and playing the drums himself. Thicker Than Water (2018) put its single "Coupe De Ville" at number one on the smooth jazz airplay chart. Since then he has released Celebrate Me Home: The Holiday Sessions (2020), a remixed Bromberg Plays Hendrix (2020), A Little Driving Music (2021), The Magic of Moonlight (2023), LaFaro (recorded live on May 1 and 2, 2023), a tribute to bassist Scott LaFaro with pianist Tom Zink and drummer Charles Ruggiero, the 2024 album Seriously with the trio BPM (guitarist Paul Brown and saxophonist Michael Paulo), and Awakening, issued on Shanachie on October 9, 2026.

Bromberg is a bassist of unusual range who plays acoustic double bass, electric bass and piccolo bass, an instrument tuned an octave higher so that he can take guitar-style melodies and solos on bass; the liner notes to Jaco, Metal and Awakening state that every guitar-sounding line on them is a piccolo bass. His acoustic playing, on an eighteenth-century Milan double bass, runs from walking swing and bebop standards to solo performances of material by the Beatles and Sting, and Wood became a reference recording for audio equipment. His catalog splits roughly evenly between acoustic mainstream jazz (It's About Time, the Wood albums, Downright Upright, Compared to That, Full Circle, LaFaro) and groove-based contemporary jazz made for smooth jazz radio (Magic Rain, You Know That Feeling, Thicker Than Water, Seriously), with rock and fusion tributes in between: Jaco Pastorius and Weather Report material on Jaco, Jimi Hendrix on Bromberg Plays Hendrix, and bossa nova on In the Spirit of Jobim, a record of Antonio Carlos Jobim songs and originals in his style. In his own account he began as a drummer, and that shows in his time feel, which he credits to his father; he has said that smooth jazz taught him to be a more melodic, storytelling improviser than a showpiece virtuoso. Much of his chart success came on Billboard's smooth jazz airplay survey, where "Cantaloupe Island" reached number 3 in 2007, while his jazz-bass credentials rest on the Getz quintet, the acoustic albums and a Grammy nomination in the contemporary jazz category.