Allan Harris was born in Brooklyn on April 4, 1956, into a family that had brought its music with it to New York. His mother, Johanna Chemina Ingram-Harris, was a trained pianist and a member of the first graduating class of New York's High School for the Performing Arts, and she wanted nothing to do with jazz. She taught her son piano for three years and made her position clear. Her sister Theodosia Ingram took the other side. Theodosia sang jazz and blues under the stage name Phoebe, won the Apollo Theater's talent competition, and quietly bought her nephew his first guitar. She had also had a child with Clarence Williams, the pianist, composer and publisher who managed Louis Armstrong, which turned a scandal into a family connection: weekends at the Williams house in St. Albans, Queens put a small boy in rooms with Armstrong, Duke Ellington, Sarah Vaughan, Ruth Brown and Martha Reeves. Harris named his publishing company Theodosia after the aunt who started it.

Sundays meant the subway from Brooklyn to Harlem. Another aunt, Kate Ingram, ran a soul-food luncheonette on Eighth Avenue at West 126th Street, a block behind the Apollo Theater, and the children sat in their own section while performers came in between matinees. Harris has said the sleeve of organist Jimmy Smith's Blue Note album Home Cookin' shows Smith standing in front of his aunt's place. His mother eventually gave in on the guitar and found him a classical teacher, and a Jimi Hendrix poster in the window of a Brooklyn barbershop settled the rest. When the family moved to the Pittsburgh area in his teens, where his father, a Navy man, kept a 600-acre horse farm, Harris went to college nearby and worked steadily, first with an R&B cover band in Atlanta, then in Miami, singing six nights a week with a twelve-piece show band.

The turn came in Miami in 1994, when Harris was 38. Singing "I Left My Heart in San Francisco" to a room that happened to include Tony Bennett, he was invited to sing at a Sophia Loren tribute the following night, handed Bennett's card, put up in New York for two weeks and given, in Harris's telling, an education in what he was missing. Bennett pushed him to stop working as a nightclub entertainer and to treat the American Songbook as an interpreter's job. Harris moved back to New York in 1995. His first records followed immediately: Setting the Standard on his own Love Productions Records in 1994, then It's a Wonderful World for the German label Mons in 1995 with a band of Benny Green, Ray Brown, Jeff Hamilton, Mark Whitfield and Claudio Roditi, and Here Comes Allan Harris and the Metropole Orchestra in 1996, cut in Hilversum with the Dutch radio orchestra under Rob Pronk. Through the late 1990s and early 2000s he worked the European big-band circuit, singing Ellington with the RIAS Big Band alongside Clark Terry and Claire Martin, with the Thilo Wolf Big Band for Bavarian radio, and with the Big Band de Lausanne in Ellington's sacred concerts.

The project that reshaped his career was his own. Cross That River, released on Love Productions in February 2006, is a ten-song cycle about Blue, a Louisiana slave who steals his master's horse, rides west and becomes one of the first Black cowboys, with songs for Buffalo Soldiers, Black Seminoles, mail-order brides and an aging gunslinger. NPR's All Things Considered covered it in August 2006, the Kennedy Center programmed it in 2008, and a second album of the cycle, Cry of the Thunderbird, followed in 2009. Harris and his wife and manager Pat Harris spent roughly a decade turning it into a stage work: a debut at the New York Musical Theatre Festival in 2009, a Chamber Music America residency grant, school use in New York and North Carolina, and finally a five-week Off-Broadway run at 59E59 Theaters in December 2017, directed by Regge Life, with a book by Allan and Pat Harris and Harris himself playing the elder Blue with a guitar. He had already been on the same stage in December 2014 in Alex Webb's Café Society Swing, a music-theatre account of the Greenwich Village club, alongside Charenee Wade and Cyrille Aimée, in a run the New York Times made a Critic's Pick.

Alongside the theatre work, Harris built the strongest run of records of his career with producer Brian Bacchus. Black Bar Jukebox (2015), cut at Sear Sound in December 2013 and January 2014, took its premise from the jukeboxes in Harlem barbershops and bars, where Elton John, John Mayer, Kenny Rankin and Acker Bilk sat next to standards without anyone finding it strange. Its rhythm section of Pascal Le Boeuf, Leon Boykins and Jake Goldbas went on to form its own band, King Pony, with Harris guesting on their 2014 debut, and the album's guest guitarist was the Israeli player Yotam Silberstein. The follow-up, Nobody's Gonna Love You Better: Black Bar Jukebox Redux (2016), pushed further into Steely Dan, Hendrix and Portuguese-language samba. The Genius of Eddie Jefferson (2018) is a straight-ahead vocalese program built with pianist Eric Reed, with Richie Cole and Ralph Moore on saxophones and Willie Jones III on drums. Kate's Soulfood (February 12, 2021), produced by Kamau Kenyatta, returned to his aunt's luncheonette and to Harlem itself, gentrification included, across ten Harris originals.

Harris has kept working from a Harlem brownstone he shares with Pat Harris, who runs Love Productions Records. In 2022, at 66, he entered the eleventh Sarah Vaughan International Jazz Vocal Competition at NJPAC and finished third behind Lucía Gutiérrez Rebolloso and Ekep Nkwelle in a field of five finalists. Two live records made at the Blue LLama Jazz Club in Ann Arbor followed: Live at Blue LLama in 2023, his first concert album in more than thirteen years, and The Poetry of Jazz in July 2025, which sets songs against recited Shakespeare, Langston Hughes, Maya Angelou, Dylan Thomas, Mary Oliver and Robert Frost. A new stage show, Harlem After Dark, premiered at Dizzy's Club in New York on January 14, 2025 and has since travelled to Umbria Jazz. On August 28, 2026 he released Swingin' Love Songs, nine previously unreleased songs by the Charleston, West Virginia writer Ike Joseph that Harris had been carrying for more than twenty years, produced by Eddie Montilla.

Harris is a baritone who sings on the low, warm end of the crooner tradition, and the three names critics reach for, Nat King Cole, Frank Sinatra and Tony Bennett, are ones he has never denied: Bennett taught him directly, and Cole has been the subject of two of his albums. What separates him from a repertory singer is that he came up as a guitarist first, learning country, soul and rock before he found jazz, and he still plays archtop electric, acoustic and resonator guitar on his own records. That background is why a Harris program can move from "My Funny Valentine" to Jimi Hendrix's "Up From the Skies" without a seam, and why his best-known original work, the Cross That River cycle, is closer to blues and Americana than to the songbook. He is also unusually willing to hand the guitar chair to someone else and concentrate on singing: on Black Bar Jukebox the guitarist for most of the record is Yotam Silberstein, while Harris keeps only one acoustic credit for himself, and on the 2016 sequel it is Freddie Bryant. As a songwriter he writes his own lyrics and publishes through Theodosia Publishing, and his originals ("Blue Was Angry," "New Day," "Shallow Man," "Secret Moments") now sit at the centre of his live sets rather than at the edges. He has won the New York Nightlife Award for Outstanding Jazz Vocalist three times, has been named a Rising Star Jazz Vocalist by DownBeat, and took Hot House Jazz Magazine's Best Male Jazz Vocalist award twice.