Antonio Hart was born September 30, 1968, in Baltimore. The music and art programs at his public school were cut while he was in ninth grade, and a friend who attended the newly opened Baltimore School for the Performing Arts got him an audition there. He had almost no jazz background and could not yet read music at the level he was attempting; he spent the night before the audition on the phone with that friend learning "Hungarian Dance No. 5" out of a book, played it and some scales for three teachers, and got the acceptance letter a week later. His training at the school was classical, and he credits his private teacher Chris Ford with taking him well past the level of an average high school player. Jazz reached him through the radio: the station at nearby Morgan State University introduced him to Grover Washington Jr. first, then Charlie Parker and Sonny Stitt. He has said the pull was partly that European concert repertoire was through-composed and left him no room to be creative, and partly that he saw very few African American players performing it.

He arrived at Berklee College of Music in Boston at seventeen, starting in the school's lowest ensembles because he knew music from a European perspective and still had to learn the jazz vernacular. He studied with saxophonists Bill Pierce, Andy McGhee, and Joseph Viola, and in his sophomore year switched to a music education major on the theory that teaching, not touring, was his real trajectory. His classmates included Mark Turner, Seamus Blake, Lalah Hathaway, and Paula Cole, and, most consequentially, trumpeter Roy Hargrove. Hargrove asked him to join his band, and Hart spent roughly three years touring with him and playing on Hargrove's first records: Diamond in the Rough (Novus, 1990), Public Eye (1991), and The Vibe (1992). The press filed them both under the Young Lions, alongside Christian McBride, Geoff Keezer, Gregory Hutchinson, Mark Whitfield, and Tim Warfield. Hart has said he nearly turned down the RCA contract he was offered at about twenty, on the grounds that he had barely played with anyone yet.

He took it, and his leader debut, For the First Time (Novus 3120-2-N), was cut at Clinton Recording Studios in New York across February and April 1991 with Mulgrew Miller on piano, Christian McBride on bass, and Lewis Nash on drums, plus Hargrove, Thomas Williams, and Bill Pierce as guests. Don't You Know I Care followed in 1992 (Novus 01241 63142-2), a quintet date with Darren Barrett, Aaron Graves, Rodney Whitaker, and Gregory Hutchinson, with Gary Bartz guesting on one track; Jimmy Heath produced it. Hart had begun a master's degree at Queens College while working the road, studying there with Heath and with Donald Byrd, and he stopped short of the doctorate he had planned because he was touring constantly. The same stretch produced The Tokyo Sessions (Novus 01241 63164 2), co-billed with Hargrove and recorded direct to two-track digital tape at Studio Sound Valley in Tokyo on December 4 and 5, 1991.

For Cannonball and Woody (Novus 01241 63162-2, 1993), cut at Systems Two in Brooklyn, was Hart's tribute to Cannonball Adderley and Woody Shaw and the largest cast he had assembled: Nat Adderley on cornet, Slide Hampton, Steve Turre, and Robin Eubanks on trombones, Craig Handy on tenor, Mark Gross on second alto, Mulgrew Miller and Carlos McKinney splitting piano, Ray Drummond and the young Israeli bassist Omer Avital on bass, and Jimmy Cobb, Victor Lewis, and Nasheet Waits rotating on drums. It's All Good (Novus, 1995) shrank the band back to a quintet, and Alto Summit put Hart in a three-alto front line with Phil Woods and Vincent Herring over Anthony Wonsey, Reuben Rogers, and Carl Allen (issued in Japan in 1995 as Alto Legacy on Key'stone and in the United States in 1996 on Milestone). Here I Stand (Impulse! IMPD-208, 1997) was the record that broke him wider: a Systems Two date with James Hurt on piano and organ, John Benitez on bass, Waits on drums, Robin Eubanks on trombone, Shirley Scott guesting on organ, and poet Jessica Care Moore reading on "Riots... The Voice of the Unheard." It brought Hart a Grammy nomination for Best Jazz Instrumental Solo.

The other half of his career has been section work in the big bands. He held a chair in the Dizzy Gillespie big bands for roughly twenty-five years, starting on second alto and moving to first after thirteen, and he recorded with Dizzy Gillespie himself during the trumpeter's final Blue Note engagement in New York on January 23 to 25, 1992, documented on To Bird with Love (Telarc CD-83316, 1992) and, five years later, Bird Songs: The Final Recordings (Telarc CD-83421). He went on to the posthumous Gillespie repertory groups, including the Alumni All-Star Big Band's Things to Come (2002) and the Dizzy Gillespie All-Star Big Band's Dizzy's Business (MCG Jazz, recorded live in Pittsburgh in 2005) under Slide Hampton's direction. He also played in the Mingus Big Band, the Duke Ellington Orchestra, the Vanguard Jazz Orchestra, Arturo O'Farrill's big band, and the Gerald Wilson Orchestra, and he spent three and a half years in Nat Adderley's quintet, a run that produced the co-billed Good Company (Challenge, recorded June 20 and 21, 1994). His longest big-band association on record is with Dave Holland: alto and flute on the Grammy-winning What Goes Around (ECM 1777, recorded at Avatar Studios in January 2001), Overtime (2004), the sextet album Pass It On (Dare2, recorded August 2007), and the octet's Pathways (Dare2, recorded live at Birdland in January 2009).

His later leader dates moved away from the Novus template. Ama Tu Sonrisa (Enja ENJ-9404 2) was recorded at Systems Two between April and July 2000 and released in 2001, adding Yosvany Terry's tenor, Steve Nelson's vibraphone, Kevin Hays's piano, three percussionists, and vocals from Claudia Acuña and Lenora Zenzalai Helm; one track is titled "Grover Washington Jr." All We Need (Downtown Sound DS 1003, recorded September 11 and 12, 2003 at Bennett Studios in Englewood, New Jersey, released June 8, 2004) brought Jimmy Heath back as a tenor guest. Blessings (Jazz Legacy Productions JLP 1501023) was cut at Tedesco Studios in Paramus, New Jersey in June 2013 and released in 2015 as an organ quartet with Bobby Floyd, guitarist Yotam Silberstein, and drummer Steve Williams, running from Brother Jack McDuff's "Rock Candy" through Frank Foster's "Shiny Stockings" and Stevie Wonder's "I Can't Help It." Alongside the jazz work he has turned up in other rooms: he plays flute on two tracks of Common's Like Water for Chocolate (MCA, 2000), and flute again on Terri Lyne Carrington's Money Jungle: Provocative in Blue (2013).

Teaching, the career he originally trained for, came back. Hart is a full professor and director of jazz studies at the Aaron Copland School of Music at Queens College, City University of New York, where he teaches jazz improvisation, combo workshop, jazz history, saxophone quartet, jazz musicianship, and private lessons, and where he had been on the faculty for twenty-two years as of 2022. He also directs the Queens Jazz Orchestra, the Flushing Town Hall big band founded in 2008 by Jimmy Heath, whom Hart calls his mentor and describes as a father figure across a thirty-year connection. He has appeared as a guest on more than a hundred recordings.

Hart's alto sound is built on the bebop lineage he set out to learn from scratch at Berklee: Charlie Parker and Sonny Stitt on the vocabulary side, Cannonball Adderley on the attack and the blues weight, and, first of all, the Grover Washington Jr. records he heard on Baltimore radio, which is why a soul-jazz strain keeps surfacing in his playing and why Blessings is an organ-quartet album. He describes himself as a student of the whole saxophone lineage rather than of one player, and credits that study with a career that has outlasted many of his Young Lions contemporaries. As a leader he has resisted settling into a single format: a straight quintet on Don't You Know I Care, a ten-piece tribute band on For Cannonball and Woody, a Latin and Afro-Caribbean percussion setting with vocalists on Ama Tu Sonrisa, an organ quartet on Blessings. His section playing is what has kept him employed in the big bands, where he is a lead alto as much as a soloist, and he doubles on soprano and flute across most of his post-1995 work.