Mulgrew Miller was born on August 13, 1955, in Greenwood, Mississippi, one of eight children (he had three brothers and four sisters) of parents who had grown up on plantations. Nobody in the family played, but there was a piano in the house, and he picked out tunes on it by ear from the age of six and took lessons from eight. As a boy he played blues and rhythm and blues at dances and gospel in churches of several denominations, although the family itself was Methodist. His first model at the keyboard was Ramsey Lewis. Around the age of 14 he watched Oscar Peterson on television's The Joey Bishop Show, a broadcast he later called life changing, the moment he knew he would be a jazz pianist; Art Tatum and Erroll Garner followed as teenage influences, and in high school he led a trio that played cocktail parties.

After Greenwood High School he entered Memphis State University in 1973 on a band scholarship, playing euphonium. There the pianists Donald Brown and James Williams introduced him to the playing of Wynton Kelly, Bud Powell and McCoy Tyner, and at a campus jazz workshop he met the trumpeter Woody Shaw, one of the instructors, who told him they would see each other again in two years. He left school in 1975, studied privately in Boston with the teacher Margaret Chaloff, played with the saxophonists Ricky Ford and Bill Pierce, and then spent a year in Los Angeles working local clubs and a church.

At the end of 1976 he was asked to fill in for the regular pianist in Duke Ellington's orchestra, by then led by the leader's son Mercer Ellington. The job was meant to last three weeks; he stayed for almost three years. In January 1980 the singer Betty Carter hired him away, and he toured with her for eight months. From 1981 to 1983 he was in Woody Shaw's band, making his studio debut on Shaw's United (1981), and in the early 1980s he also accompanied the singer Carmen Lundy and worked with the tenor saxophonist Johnny Griffin. On the recommendation of Terence Blanchard and Donald Harrison he joined Art Blakey's Jazz Messengers in 1983 and stayed until 1986; the Messengers years, he said, matured his playing and steadied his confidence, and they established his name. His first album as a leader, Keys to the City (recorded June 1985), opened a run of releases for Landmark that continued with Work! in 1986.

When he left Blakey in 1986 he became the pianist in Tony Williams's new quintet from its formation, and he stayed until the band broke up around 1993. Between Williams tours he led his own groups. The first, formed in 1987, was Wingspan, named as a dedication to Charlie Parker; it lasted through many personnel changes and carried much of his own writing. A second, Trio Transition, paired him with bassist Reggie Workman and drummer Freddie Waits. In 1989 he joined three other pianists as the Contemporary Piano Ensemble, which recorded a tribute to Phineas Newborn Jr. and played together on four pianos until 1996, and the same year he moved his family to Palmer Township in Pennsylvania's Lehigh Valley. He went to the Soviet Union in 1990 as pianist in Benny Golson's band for the first Moscow International Jazz Festival, toured in 1992 with the septet New York Jazz Giants, recorded with the singers Dianne Reeves and Cassandra Wilson, and from 1993 worked with the tenor saxophonist Joe Lovano. His first album for Novus, Hand in Hand, appeared in 1993.

After turning 40 he pulled back from the constant sideman work of the late 1980s and put his own music first. He still reunited with Williams for the drummer's last album, Young at Heart (1996); toured Japan in 1997 with the ten-pianist troupe 100 Golden Fingers; and in 1999 recorded a duo album of Ellington and Jimmy Blanton repertoire with the Danish bassist Niels-Henning Ørsted Pedersen, with whom he toured Europe the next year. From 2002 the Maxjazz label released a run of his live trio recordings, and that year he also joined bassist Ron Carter's Golden Striker Trio with guitarist Russell Malone. In 2003 he wrote The Clearing in the Woods for the Dayton Contemporary Dance Company, and in the mid-2000s he joined Dave Holland's band, which grew from a quintet to a sextet. He became director of jazz studies at William Paterson University in 2005, received an honorary doctorate from Lafayette College in 2006, and was the college's artist in residence in 2008. In 2010 he joined John Scofield's new band and had a minor stroke, after which he changed his diet and cut back on touring and recording. In February 2012 he played with Klüver's Big Band in Denmark, in autumn 2012 he performed as a duo with pianist Kenny Barron, and that winter he toured Europe in a quintet led by Yusef Lateef and Archie Shepp.

On May 24, 2013, he was admitted to Lehigh Valley Hospital-Cedar Crest in Allentown, Pennsylvania, after another stroke, and he passed away there on May 29, at the age of 57. He was survived by his wife, a son, a daughter and a grandson. He made more than 15 albums under his own name and appeared on more than 400 for other leaders, and the live and duo recordings issued since his death (among them The Duo: Live! with Pedersen, In Harmony with Roy Hargrove, The Art of Piano Duo: Live with Barron, and Solo in Barcelona) have kept adding to the catalogue.

Miller built his playing on the full-handed swing of Oscar Peterson and Ramsey Lewis, then opened it up with the freer harmonic ideas of McCoy Tyner, ending with a style that influenced pianists from the 1980s on. Ben Ratliff of The New York Times found him hard to pin down as a composer, as he was as a player, and Ted Panken wrote that he could draw beauty from pentatonic scales and odd intervals while driving the music with a joyous, unceasing beat, with church and blues inflections running through the lines. John Fordham of The Guardian heard Peterson's fluency and percussive chording in his playing along with glimpses of Tyner's harmonic freedom, and argued that he was much more than the hard bop pianist he was often labeled. His compositions for his own bands show the imprint of Tony Williams's writing and arranging, as the opening "Grew's Tune" on Hand in Hand illustrates. He took a conservative view of standards, believing in playing the melody as written and treating a solo as a way to improve it, and he almost never transcribed recordings, which he thought slowed his learning but let him reach his own understanding of the music. Colleagues held him in high regard: the pianist Geoffrey Keezer decided to become a pianist after hearing him in 1986, the vibraphonist Warren Wolf credited him with early help and with a direct link to the Art Blakey tradition of giving other players room, and Robert Glasper wrote and recorded "One for 'Grew" in tribute. Miller observed that players working in his vein were regarded as out of date, and he was wary of what he called interview music, work that gets attention for being obviously different.