Kevin Hays was born May 1, 1968, in New York City and raised in Greenwich, Connecticut, the youngest of four children. His father was an amateur pianist, and Hays began lessons at six, initially self-taught before studying with Lou Stein and attending the Interlochen music camps. Rock music was his first pull, but a jazz interest took hold in his early teens, and by 1982 he was already playing locally. He started performing in New York City in 1985 while still in high school, working in saxophonist Nick Brignola's band, and attended the Manhattan School of Music for a single semester in 1986 before leaving to focus on performing full time.

His debut as a leader, El Matador, was recorded in August 1990 for the Japanese label Jazz City (released 1991) with saxophonist Steve Wilson, bassist Scott Colley, and drummer Bill Stewart — and a guest appearance from tenor saxophonist Joe Henderson, whose own career is covered in full in his JazzProfiles.com profile. It was the first of what would become a decades-long, on-and-off working relationship: Hays and Henderson went on to tour together internationally in the years that followed. Three albums for SteepleChase Records rounded out his early run as a trio and small-group leader — SweetEar (1991, with Eddie Henderson, Vincent Herring, James Genus, and Joe Chambers), Ugly Beauty (1991, with Larry Grenadier and Jeff Williams), and Crossroad (1992, with Scott Wendholt, Freddie Bryant, Dwayne Burno, and Carl Allen).

A three-album run for Blue Note Records followed and remains the best-known stretch of his catalog. 7th Sense (1994), produced by guitarist John Scofield and featuring Seamus Blake, Steve Nelson, Doug Weiss, and Brian Blade, drew a review from The New York Times calling it "a jolt of joy" and was named one of Musician Magazine's "Top 40 Jazz Releases of the Year"; drummer Brian Blade has separately cited the session as one of the most memorable of his career. Go Round (1995) brought in Billy Hart on drums, and Andalucia (1996-97) paired Hays with Ron Carter and Jack DeJohnette — as strong a rhythm section as a young pianist could ask for. The Scofield connection deepened in 1996, when Hays joined the guitarist's touring quintet behind the Quiet album, alongside Seamus Blake, Larry Grenadier, and Bill Stewart; Scofield, whose own career is covered in full in his JazzProfiles.com profile, later called Hays "all encompassing. Phenomenally so!" Hays's promotional biography also lists world tours during this period with Sonny Rollins, Roy Haynes, and singer-songwriter James Taylor — the kind of high-profile sideman work that built his reputation well beyond his own recordings as a leader.

From the early 2000s on, Hays led a long-running working trio with bassist Doug Weiss and drummer Bill Stewart — a partnership that stretched across roughly fifteen years and multiple albums, including What Survives (recorded 2001, released 2002 on PinonDisk), Fear of Roaming (2004, Fresh Sound New Talent), For Heaven's Sake (recorded January 2005, released 2006), The Dreamer (2006-07, ArtistShare), and You've Got a Friend (2007-08). For Heaven's Sake, dedicated entirely to the Great American Songbook, was the standout of that run: it won the "Coup de Coeur" prize from France's Académie Charles Cros and a "Best of the Year" nod from The New Yorker. Alongside the trio records, Hays built a parallel career as a solo pianist, releasing Piano Works III: Open Range (recorded 2004, released on the German label ACT) and Variations (2010-11, Pirouet) — unaccompanied recordings that showcase the harmonic language critics trace to Paul Bley's pedal-driven, "clipped" phrasing.

Hays has never confined himself to the piano trio. Dawning (2013, Palmetto), recorded with sitarist Shujaat Husain Khan, tabla player Abhiman Kaushal, and vocalist Katayoun Goudarzi, pushed into Indian classical territory through his ensemble Sangha. Modern Music (2011, Nonesuch) paired him in a genuine two-piano co-billing with Brad Mehldau, playing Steve Reich, Ornette Coleman, and Philip Glass alongside originals in arrangements by composer Patrick Zimmerli. And in 2019 he recorded Hope, a duo album with guitarist Lionel Loueke, extending a catalog of unlikely instrumental pairings.

The most distinctive turn in Hays's later career has been toward singing. New Day (2015, Sunnyside) introduced his New Day Trio, with bassist Rob Jost and drummer Greg Joseph, plus guest turns from harmonica player Grégoire Maret and guitarist Tony Scherr — Hays's first outing as a full-fledged singer-songwriter, moving through funky, folk-rock-inflected originals rather than jazz standards. North (2016) continued the trio's songbook. Reviewers were careful to note the shift was additive rather than a departure: Hays remained, in the same period, "one of the great acoustic piano players of his generation," now simply revealing a second, unexpected voice.

Hays's sideman resume in the 2010s and 2020s runs in parallel to his own catalog. He was a member of the Steve Gadd Band from 2017 to 2019 and co-wrote several compositions on the group's self-titled 2019 album — the record that won the Grammy Award for Best Contemporary Instrumental Album, the source of the "Grammy Award-winning" credit that appears in his own promotional bios, distinct from any Grammy attached to his own leader recordings. He has also continued to work with Chris Potter, whose own career is covered in full in his JazzProfiles.com profile, and with drummer Al Foster, whose own career is covered in full in his JazzProfiles.com profile, in the Al Foster Quartet.

His most recent leader albums have paired him with bassist Ben Street and drummer Billy Hart as a working trio: All Things Are (2021, Smoke Sessions), recorded live and crowdless at New York's Smoke Jazz Club over the first weekend of December 2020 to celebrate Hart's 80th birthday, and Bridges (2023, Smoke Sessions), which set originals by Hays and Hart alongside music by Wayne Shorter, Bill Frisell, the Beatles, and Milton Nascimento. In between came the self-released American Ballad (2022) and the genre exercise Whole Lotta Love: The Music of Led Zeppelin (2021). More recent releases include Lingering (2024) and The Wait (2025, Clap Your Hands), a duo album with drummer/vibraphonist Jorge Rossy — whose own career is covered in full in his JazzProfiles.com profile — mixing four Hays originals and two Rossy compositions with covers of Monk, Bernstein, and Milton Nascimento. A live Village Vanguard trio recording alongside bassist Thomas Morgan and drummer Brian Blade is slated for spring 2027, an output that shows no sign of slowing. Drummer Colin Stranahan, whose own career is covered in full in his JazzProfiles.com profile, has been a recurring member of Hays's touring trio in recent years, documented across venue bookings from San Diego's Athenaeum to Oakland's Piedmont Piano Company.

Hays's playing is often described as linear and harmonically dense, with a pedal technique that produces a clipped, sustained sound that critics trace to the early work of Paul Bley. That foundation has carried him across an unusually wide range of settings without ever losing its identity — from the hard-driving post-bop of his SteepleChase and Blue Note trio records, through the rhythm-section pairings with Ron Carter, Jack DeJohnette, and Billy Hart that defined his 1990s output, to the more exploratory, world-music-inflected projects like Dawning and the two-piano dialogue of Modern Music. Where he has departed furthest from the piano-trio mainstream is in his singing: on New Day and North, Hays sets aside the interpreter's role for jazz standards and writes and sings his own folk-rock-leaning songs, a strand of his output that sits alongside, rather than replaces, his standing as one of his generation's most consistently recorded straight-ahead pianists.