Raised in Gurnee, north of Chicago, Brian Simpson began playing piano at an early age, and owing to his father's record collection was inclined toward jazz from the outset. Oscar Peterson was a notable influence, although he also listened to jazz guitarists such as Wes Montgomery and Joe Pass. Simpson studied at Columbia College and at Northern Illinois University, where he played keyboards in various ensembles from small groups to big bands. With the university's big band, he was widely heard and drew appreciative attention.
After graduation Simpson relocated to Los Angeles, where he played jazz informally for a while, but was mainly active as an accompanist for pop and R&B singers, including Sheena Easton and Janet Jackson. Meanwhile, he was composing songs and was co-writer of 'The First Time', which the soft soul trio Surface took to the top of the Adult Contemporary chart in 1991. During the rest of the 90s Simpson gradually moved more closely to the jazz scene; in particular he became musical director for Dave Koz. He also played in the all-star band Koz led for Rendezvous Records.
Among the artists with whom Simpson has worked in clubs, at concerts and festivals, and sometimes recording are Gerald Albright, Larry Carlton, Stanley Clarke, Billy Cobham, George Duke and George Howard. His own name dates have been infrequent, but include 1995's Closer Still and 2005's It’s All Good. The title track of the latter enjoyed notable success on US smooth jazz radio.