A native San Diegan and graduate of Point Loma High, Jason Scheff got his local start with bands like the People Movers and M&Ms. His father Jerry Scheff was a studio bassist who played for Bob Dylan, Elvis Presley, and the Doors.

While playing L.A. studios in the mid-1980s, Scheff auditioned for the band Chicago, eventually replacing Peter Cetera as their lead singer. The first Chicago album to feature Scheff was Chicago 18.

As of 2011, Scheff was married with four children and living in Nashville. In October 2016, after over thirty years with Chicago, he left that group.

Scheff performed with Rush guitarist Alex Lifeson in Malibu on October 28, 2018 as part of the 11th annual Scott Medlock-Robby Krieger Golf Classic's All-Star Concert to benefit St. Jude Children's Research Hospital at the Saddlerock Ranch, playing the Rush classics "Limelight", "The Spirit Of Radio," and "Freewill."

The following year, It Was Fifty Years Ago Today - A Tribute To The Beatles White Album featured Scheff touring alongside Badfinger's Joey Molland, Christopher Cross, Todd Rundgren, and Micky Dolenz, kicking off September 21, 2019 in Atlantic City, NJ.

In 2022, Scheff joined an all-star roster of musicians teaming up to launch the It Was Fifty Years Ago Today: A Tribute to The Beatles tour. The shows featured Todd Rundgren, Christopher Cross, Joey Molland of Badfinger, Jay DeMarcus of Rascal Flatts, Denny Laine (founding member of The Moody Blues and Wings), and Scheff performing their hits plus selected songs from The Beatles' albums Rubber Soul and Revolver.