Gregory Porter was born on November 4, 1971, in Sacramento, California, and grew up in Bakersfield, one of eight children raised by his mother, Ruth, a church minister. His father was largely absent. He began singing in church as a child and learned a great deal about phrasing from his mother's Nat King Cole records; when he was five or six she told him he sounded like Cole. After graduating from Highland High School in 1989 he went to San Diego State University on a football scholarship as a lineman. A shoulder injury in his junior year ended that career, and it was in San Diego that he met the producer and arranger Kamau Kenyatta, who has worked with him ever since. His mother died of cancer when he was 21, and from her deathbed she urged him to keep singing.

After college he moved to New York, where he was a member of the original Broadway cast of It Ain't Nothin' But the Blues and wrote a semi-autobiographical musical, Nat King Cole & Me, staged in 2004 for an eight-week run in Colorado. In 2004 he also settled in the Bedford-Stuyvesant section of Brooklyn with his brother Lloyd, cooking at Lloyd's restaurant Bread-Stuy, where he also sang. He built a following at neighborhood rooms such as Sista's Place and Solomon's Porch and then at St. Nick's Pub in Harlem, where a weekly residency grew into the working band that became his touring group.

His first two albums came out on Motéma. Water was recorded on August 19 and 20, 2009, at 58 North Six Media Lab in Brooklyn, produced by Kenyatta, with pianist Chip Crawford and alto saxophonist James Spaulding among the players, and released on May 11, 2010; it was nominated for the Grammy for Best Jazz Vocal Album. Be Good (February 2012) was recorded in Brooklyn on June 20 to 22, 2011, and produced by Brian Bacchus, with Crawford, bassist Aaron James, drummer Emanuel Harrold, saxophonists Yosuke Sato and Tivon Pennicott, and trumpeter Keyon Harrold. Most of the songs were his own, and "Real Good Hands" earned a Grammy nomination for Best Traditional R&B Performance.

Porter signed with Blue Note on May 17, 2013. Liquid Spirit, recorded at Sear Sound in New York on March 28 to 30 and April 15, 2013, and produced by Bacchus, came out in Europe on September 2, 2013, and in the United States on September 17. It won the Grammy for Best Jazz Vocal Album at the 56th ceremony in January 2014, reached number 9 on the UK album chart, and was certified Platinum there in 2016, a sales level rare for a jazz record. In 2015 he was the featured vocalist on "Holding On," the first single from the British duo Disclosure's album Caracal. Take Me to the Alley (May 6, 2016), produced by Porter and Kenyatta from sessions at Sear Sound in New York and Capitol Studio B in Hollywood in the autumn of 2015, won him a second Grammy for Best Jazz Vocal Album in 2017, and on June 26, 2016, he played the Pyramid Stage at the Glastonbury Festival.

Nat King Cole & Me (October 27, 2017) was the tribute he had been planning for years: Vince Mendoza arranged and conducted a 70-piece orchestra at AIR Studios in London, and the album entered the UK chart at number 3, his highest debut there. A live album with the London Studio Orchestra, One Night Only, recorded at the Royal Albert Hall in April 2018, followed in November 2018. All Rise (August 28, 2020) returned to his own songs, produced by Troy Miller and Kenyatta with London Symphony Orchestra strings and horn arrangements by Etienne Charles, and was nominated for the Best R&B Album Grammy. Christmas Wish, recorded in Abbey Road's Studio 1 and produced by Miller, appeared on November 3, 2023, and was nominated for Best Traditional Pop Vocal Album. In December 2025 his song "Good Goodbye" opened the soundtrack of Kate Winslet's Netflix film Goodbye June, and a tenth-anniversary edition of Take Me to the Alley was issued in 2026.

Porter is a baritone whose sound joins the gospel music of his childhood to the unhurried storytelling of Nat King Cole, and unlike many jazz singers of his generation he writes most of his own repertoire. In a 2014 interview he named Donny Hathaway, Nat King Cole and Bill Withers as singers whose gospel roots he recognized as his own, and he pointed to Ray Charles in the same vein. Songs such as "Be Good (Lion's Song)," "On My Way to Harlem," "1960 What?" and "Liquid Spirit" mix love songs, social commentary and church-derived choruses over a small-group jazz backing. When Water appeared, JazzTimes set his clarity of tone beside Sammy Davis Jr. and his technique beside Kurt Elling, and The Guardian later noted how uncompromising the gospel core of Take Me to the Alley remained beneath its smooth surface. His records sit at the meeting point of jazz, soul and gospel, which explains both his two Grammys in the jazz vocal category and nominations in R&B and traditional pop, as well as top-ten placings in the UK, Germany and the Netherlands that are unusual for a jazz singer.