Brad Mehldau was born Bradford Alexander Mehldau on August 23, 1970, in Jacksonville, Florida, and adopted into a family that relocated twice in his childhood: first from Roswell, Georgia to Bedford, New Hampshire in 1975, then to West Hartford, Connecticut when he was ten. A piano sat in the house the whole time. He gravitated to pop and rock first, then a new teacher introduced him to classical repertoire around age ten. Jazz arrived at fourteen, through John Coltrane and Oscar Peterson records; Keith Jarrett's solo concert recordings from Bremen and Lausanne showed him what the instrument alone could do.

At Hall High School in West Hartford he played in the concert jazz band, started transcribing solos off records, and by fifteen was gigging weekly at a local club and playing weddings, often alongside fellow student Joel Frahm. He won Berklee College of Music's Best All-Round Musician award for high schoolers during his junior year. In 1988 he moved to New York on a partial scholarship to study at the New School, working under pianists Fred Hersch, Junior Mance, and Kenny Werner and drummer Jimmy Cobb. His first professional touring credit came in 1989 and again in 1991, on the road with saxophonist Christopher Hollyday's band; his first recording, Hollyday's The Natural Moment, was taped in January 1991. He graduated from the New School in 1993.

From 1993, Mehldau spent eighteen months touring in saxophonist Joshua Redman's quartet. The band's 1994 studio album, MoodSwing, raised his profile substantially — it remains the credit most often cited as the true launching point of his career. That same year he formed the Brad Mehldau Trio with bassist Larry Grenadier and drummer Jorge Rossy, a partnership that would define his sound for the rest of the decade. Introducing Brad Mehldau followed in 1995 on Warner Bros., well received but modest next to what came after: The Art of the Trio, Volume One (recorded 1996, released 1997) drew the kind of notice that made critic John Fordham call him "the next great keyboard star of jazz." Four more numbered volumes followed through 2001 — Live at the Village Vanguard (1998), Songs (1998, closing with covers of Nick Drake's "River Man" and Radiohead's "Exit Music (For a Film)"), Back at the Vanguard (1999), and Progression (2001) — alongside Alone Together (1997), a trio session co-led with Lee Konitz and Charlie Haden. Mehldau has been open about struggling with heroin addiction through most of the 1990s; he moved to Los Angeles around 1996 to get clear of it, and has described what followed once he stopped using as "a rush of creativity that had been held in check."

Elegiac Cycle (1999), his first entirely solo record, drew on his interest in Brahms, Schubert, and Schumann — nineteenth-century German Romanticism filtered through a jazz pianist's hands. Places (2000) mixed trio and solo tracks, all originals inspired by cities on tour. In 2001 he scored the French film Ma femme est une actrice, his first film work, and first performed with saxophonist Wayne Shorter, a relationship that led to his appearance on Shorter's Grammy-winning Alegría in 2003. Largo (2002), produced by Jon Brion with rock musicians, classical instrumentalists, and electronic overdubs folded into the sound, marked his first real break from pure piano-trio format; as of 2010 it remained his best-selling record, and saxophonist Joshua Redman has called it the album younger musicians most often name as a defining influence. Live in Tokyo (recorded 2003, released 2004) became his Nonesuch Records debut.

In autumn 2004, Mehldau put together a quartet with saxophonist Mark Turner, Grenadier, and drummer Jeff Ballard, and that summer toured Europe with a band that included guitarist Kurt Rosenwinkel and Joshua Redman. The following year, Ballard formally replaced Rossy in the trio — critic Ray Comiskey noted the change gave the group "a harder edge" without upending its identity — starting with Day Is Done (2005). That same year Mehldau premiered a Carnegie Hall-commissioned song cycle for soprano Renée Fleming, released in 2006 as Love Sublime, setting poems by Rilke and Louise Bogan — his first classical/art-song crossover record. From 2005 he also began an extended collaboration with guitarist Pat Metheny, releasing two albums from a single December 2005 session (Metheny Mehldau, 2006, and Quartet, 2007) and touring together worldwide in 2007. In March of that year he premiered his own piano concerto, "The Brady Bunch Variations for Piano and Orchestra," with the Orchestre national d'Île-de-France in Paris.

Carnegie Hall commissioned a second song cycle in 2009, this time for mezzo-soprano Anne Sofie von Otter; they premiered Love Songs together that year and recorded it in 2010, the same year Nonesuch released Highway Rider — a double-disc set combining his trio, drummer Matt Chamberlain, guest saxophonist Joshua Redman, and a 28-piece chamber orchestra, again produced by Jon Brion. During 2010-11 Mehldau held Carnegie Hall's Richard and Barbara Debs Composer's Chair, the first jazz musician to do so. Ode and its covers companion Where Do You Start (both 2012, recorded 2008 and 2011) marked the Ballard-era trio's return to the studio after several years away.

In 2013 Mehldau began touring with drummer Mark Guiliana as Mehliana, an electronics-driven duo pushing his playing into synthesizers and Fender Rhodes over Guiliana's live-but-programmed-sounding drumming. Their album, Mehliana: Taming the Dragon, arrived on Nonesuch in February 2014 and earned Mehldau a Grammy nomination for Best Improvised Jazz Solo on the track "Sleeping Giant"; the duo expanded to a trio with guitarist John Scofield for a 2016 tour. 10 Years Solo Live (2015) gathered a decade of concert recordings, while Blues and Ballads (2016) reunited the Grenadier/Ballard trio in the studio. From around 2015 Mehldau began writing pieces in dialogue with Bach's Well-Tempered Clavier, a project that became After Bach (2018) and, six years later, After Bach II (2024). Seymour Reads the Constitution! (2018) — its title drawn from a dream in which actor Philip Seymour Hoffman read to him — was the trio's next studio record.

Finding Gabriel (2019), a thematically unified set featuring Mehldau on piano, synthesizers, and vocals alongside guests including Ambrose Akinmusire, Kurt Elling, and Mark Guiliana, won the 2020 Grammy for Best Jazz Instrumental Album. During the COVID-19 lockdowns of 2020, sheltering with his family in Amsterdam, he wrote and recorded Suite: April 2020 and a live solo set of Beatles songs taped at the Philharmonie de Paris that September, eventually released in 2023 as Your Mother Should Know: Brad Mehldau Plays the Beatles. Jacob's Ladder (2022), built largely from sessions recorded remotely during the pandemic, explored the progressive-rock influences of his youth — Mehldau has described it as tracing "a breakdown... the descent, the way through and the way out." Also in 2022 he recorded The Folly of Desire, a second major song cycle, this time for tenor Ian Bostridge, released the following year on PentaTone. Redman, Mehldau, bassist Christian McBride, and drummer Brian Blade reunited the MoodSwing quartet twice in this period, for RoundAgain (2020) and LongGone (2022), their first recordings together since 1994.

Mehldau published a memoir, Formation: Building a Personal Canon, Part 1, in 2023. Après Fauré and After Bach II (both 2024) continued his dialogues with classical composers, and Better Angels (2024) reunited him with guitarist Peter Bernstein — a musician he'd first recorded with in 1993 — for a quartet date on Smoke Sessions. His most recent album, Ride into the Sun (2025), sets ten Elliott Smith compositions alongside four Mehldau originals with chamber orchestra, and earned a Grammy nomination for Best Alternative Jazz Album. He is married to Dutch jazz vocalist Fleurine, whom he met in 1997; they have three children and have divided their time between Amsterdam and New York.

Mehldau's own list of direct influences includes pianist Larry Goldings for "his full approach to the instrument," Kevin Hays for alternative harmonies, and guitarist Peter Bernstein for melodic phrasing; he has named Fred Hersch as his single biggest influence on solo piano playing. His technique includes independent, simultaneous melodic lines in each hand — an improvised counterpoint — unusual meters (he has played "All the Things You Are" in 7/4), and a reach wide enough for tenth and eleventh intervals. He spent roughly a year working out his rhythmic vocabulary directly with drummer Jorge Rossy in the Trio's early days.

Critics tend to place him between Keith Jarrett and Bill Evans: Evans's harmonic voicings, Jarrett's free but lyrical improvising. What sets him apart is how naturally pop and rock repertoire sits inside his jazz vocabulary — Radiohead, Nick Drake, Nirvana, Oasis, and the Beatles have all passed through his trio and solo recordings without, as more than one critic has put it, trivializing either side of the equation. Critic Nate Chinen called him, in 2013, "the most influential jazz pianist of the last 20 years"; pianist Ethan Iverson has said Mehldau was the principal influence on his own generation of players starting in the late 1990s. Pianist Gerald Clayton put it plainly: "He brought in a new feel and sound in jazz. I don't know a single modern pianist who hasn't taken something from Brad."