Joanna MacGregor was born in Willesden, North London, on July 16, 1959. Her mother was a piano teacher and as a child Joanna was exposed to all types of music. She played the piano and also took an interest in violin and guitar. From 1978-1981 she studied music at New Hall, Cambridge, where her teachers included composer Hugh Wood. She had further study at the Royal Academy of Music in London with pianist Christopher Elton and at the Van Cliburn Piano Institute.
In 1985 MacGregor was chosen for sponsorship by the Young Concert Artists' Trust. She gradually drew notice from her many concert successes and was signed to a contract by Collins Classics. Among her first recordings for the label was a 1991 CD, MacGregor on Broadway, a collection of works by Gershwin, Kern, Fain, Warren, Porter, Arlen, and Rodgers. She followed with a string of successful recordings for Collins, including a 1994 disc of solo works by Bartok, Debussy, and Ravel. From 1997-2000 she served as Professor of Music at London's Gresham College. In 1998 MacGregor founded her own label, SoundCircus, which eventually became affiliated with Warner Classics. MacGregor debuted as a conductor in 2002 with the Britten Sinfonia and has since regularly conducted the ensemble in concert, often from the keyboard.
Since 2006 MacGregor has served as artistic director of the Bath International Music Festival. Her 2008 CD Gershwin Piano Classics and Broadway Songbook on Regis, was another recording success. In 2010 Faber Music issued MacGregor's Exploring the Piano: Repertoire Book, part of her series of music books for children that had begun in 2000. From September, 2011 MacGregor has served as head of the keyboard department at the Royal Academy of Music in London.