Brian Simpson was born on May 11, 1961, and grew up in Gurnee, Illinois, in a musical house. His father was a jazz fan, and his brother and sister both played instruments. He started piano at ten. By his own account he first preferred the sound of jazz guitar, and the pianist who shaped his taste was Oscar Peterson. He earned a music degree in piano from Northern Illinois University, where Discogs credits him as piano soloist on two LPs by the university's jazz ensemble, Live at Montreux (recorded at the Montreux International Jazz Festival on July 17, 1984) and Jazz Lives (1985), and as composer and arranger of one piece on the first.

After graduating he moved to Los Angeles and fell into the late-night session scene, playing with the saxophonists Everette Harp and Boney James, the guitarist Norman Brown and Gerald Albright. He then spent a stretch away from jazz as a touring keyboardist for pop singers, among them Teena Marie, Sheena Easton and Janet Jackson, whom he accompanied on a world tour. In the studio he is credited with keyboards and drum programming on "Shower Me With Your Love" from Surface's 2nd Wave (1988). He is also credited as a writer, with Surface's Bernard Jackson, of "The First Time," and plays keyboards and programs the drums on it. The song was released in September 1990 as the lead single from the trio's third album, 3 Deep, and reached No. 1 on the Billboard Hot 100 in 1991 for two weeks, spent a week at No. 1 on the R&B chart and two weeks at No. 1 on the adult contemporary chart, and went gold.

In 1990, according to his official biography, a call from George Duke began a decade of touring and production work with the keyboardist, and that tenure led to work with James Ingram, Anita Baker, Dave Koz and the bassist Wayman Tisdale. His biographies also list tours with Stanley Clarke, Larry Carlton and Billy Cobham. AllMusic dates his work as musical director for Koz to the late 1990s, and a venue biography in 2024 still described him as Koz's musical director of fifteen years. An All About Jazz biography adds about a decade as musical director of The Smooth Jazz Cruise.

His own records came late. Closer Still (Noteworthy Records, 1995) was recorded and produced by Simpson, with four tracks co-produced by Oliver Wendell, a producer who returns on several later albums. It's All Good (Rendezvous Entertainment, 2005) was his breakthrough, with Koz on tenor saxophone and Harp on alto as guests; it reached No. 37 on Billboard's jazz albums chart, and "Saturday Cool" reached No. 15 on the smooth jazz songs chart. Above the Clouds (Rendezvous, 2007) brought in Michael Brecker, Duke, Koz, Chuck Loeb, Tisdale and Kirk Whalum and reached No. 21. With South Beach (Shanachie, 2010), the first of his albums for the label that has issued every one since, he reached No. 14, with Duke on synthesizer, Euge Groove on tenor saxophone and Peter White on guitar.

Just What You Need (2013) added Gerald Albright, Marc Antoine, Jonathan Butler, Koz and Elan Trotman; its title track reached No. 3 on the smooth jazz songs chart and the album reached No. 6 on the jazz albums chart. Out of a Dream (2015, released February 17) features Jonathan Fritzén, Norman Brown, the singer Maysa and Najee, and reached No. 8. Persuasion (2016) has Boney James and Peter White among its guests. Something About You (2018) includes "Morning Samba." Unified (2020), co-billed with the guitarist Steve Oliver, entered at No. 21 on the jazz albums chart. All That Matters (2021) has guest spots for Najee, Nicholas Cole and Oliver, and Soul Connection (2023) followed. Midnight Groove (2025) adds the trumpeter Keyon Harrold on the title track, the tenor saxophonist Isaiah Collier and the guitarist Antonio Gomez. His official biography calls Midnight Groove his twelfth CD.

He is Los Angeles-based and tours widely. His official biography lists 2019 dates in Japan, Australia, Korea, Indonesia, the Philippines, Spain, the United Kingdom, Portugal and South Africa, and describes him as the veteran music director of many jazz events. SFJAZZ presented him with the saxophonist and singer Grace Kelly on September 16, 2026, and he is booked at Yoshi's in Oakland on November 15, 2026.

Simpson is a smooth jazz and R&B keyboardist first, and the profile says so plainly. His records are built on mid-tempo grooves, singable piano and synthesizer melodies and a guest saxophonist or guitarist in the lead role, and his radio hits come from the smooth jazz format. AllMusic files him under jazz with a style of crossover jazz and describes a sound that blends jazz, pop and R&B; Wikipedia lists smooth jazz, contemporary jazz and R&B as his genres. He describes contemporary jazz himself as a fusion of jazz and R&B. Reviewers split on the result. All About Jazz's Jeff Winbush found three of his albums from 2013 to 2016 pleasant and polished rather than challenging, while George W. Harris of Jazz Weekly compared the lyrical spaciousness of Midnight Groove to Antonio Carlos Jobim and singled out the trumpet of Keyon Harrold on the title track.

The jazz connection is real but specific. He studied piano at a university with a working jazz ensemble, names Oscar Peterson as the pianist who formed him, spent about a decade working with George Duke, has toured with Stanley Clarke, Larry Carlton and Billy Cobham, and has put Michael Brecker, Keyon Harrold and Isaiah Collier on his own albums. His billings, though, are mostly the smooth jazz circuit of Dave Koz, Gerald Albright, Peter White and Najee, and his pop credits, from Surface to Janet Jackson, are the other half of the career.