Grant Stewart was born June 4, 1971, in Toronto, Canada, exposed early to Charlie Parker, Wardell Gray, and Coleman Hawkins by his father, a high school English teacher and semiprofessional guitarist who often played alongside him. He began on alto saxophone at ten, and at fourteen was invited by Toronto bandleader Pete Schofield to play professionally in his big band. At seventeen he switched to tenor, soon playing with Pat Labarbara and Bob Mover, whom Stewart considers one of his greatest teachers, alongside Sonny Rollins, John Coltrane, Don Byas, and Lester Young as key influences.

Moving to New York at nineteen, he began studying and performing with Donald Byrd, Barry Harris, whose own career is covered in full in his JazzProfiles.com profile, and Joe Lovano. A hard-swinging tenor saxophonist steeped in the jazz tradition, Stewart has performed with major figures including Clark Terry, Etta Jones, Jimmy Cobb, Harold Mabern, Louis Hayes, Curtis Fuller, Brad Mehldau, Bill Charlap, Lewis Nash, Peter Washington, and Peter Bernstein, and toured North America, Europe, Japan, Brazil, and Taiwan. He was among the first musicians to perform at the historic Hermitage Museum in St. Petersburg, Russia, and has been featured at the Guggenheim Museum's jazz series alongside drummer Jimmy Cobb.

His first album as leader, Downtown Sounds, was recorded December 27, 1992, on the Criss Cross label. He has eight releases as leader, two as co-leader with fellow tenor saxophonist Eric Alexander, and has appeared on trumpeter Bruce Harris's debut album, Beginnings (2017), whose own career is covered in full in his JazzProfiles.com profile.

Stewart's mentorship under Barry Harris in New York, combined with his father's early grounding in Charlie Parker, Coleman Hawkins, and Wardell Gray, made him one of the most authentically hard-swinging tenor saxophonists to emerge from the Canadian jazz diaspora, carrying the tradition forward for a new generation.