Julian Clifford Mance Jr. was born October 10, 1928 in Evanston, Illinois, just north of Chicago. His father, also named Julian, played stride and boogie-woogie at home and started teaching the boy at five; formal lessons followed at eight. The "Junior" that distinguished father from son at the keyboard became the name he carried for seventy years of professional work. His mother wanted him at Northwestern studying medicine. He enrolled instead at Roosevelt College in Chicago as a music major and lasted about a year, suspended after being caught playing jazz in a practice room. He spent the suspension working in New York with tenor saxophonist Gene Ammons, whose Chicago band he had joined in 1947 at eighteen, and who put him on record for the first time that September.

The Ammons job led directly to the two encounters that made him. In 1949 Lester Young came to hear Ammons at Chicago's Congo Lounge on a night when Young's own pianist had missed a flight; assuming Mance was a substitute rather than Ammons's regular man, Young hired him on the spot, and Mance recorded with him for Savoy that year. He worked on and off with Young into 1951 and reunited with Ammons for Prestige dates alongside Sonny Stitt in 1950. Then the draft: called up in 1951 and two weeks from shipping to Korea, Mance was pulled out of an infantry assignment by Cannonball Adderley, then running an Army band, and installed in the 36th Army Band at Fort Knox as its company clerk. He was discharged in 1953 and went straight back to Chicago, where he took the piano chair in the house rhythm section at the Bee Hive with bassist Israel Crosby and drummer Buddy Smith, backing Charlie Parker, Coleman Hawkins, Eddie "Lockjaw" Davis and Stitt as they passed through.

Parker told him to move to New York, and in 1954 he did, stepping into Dinah Washington's group after Wynton Kelly was drafted. He toured with Washington for roughly two years and credited her arranger, Jimmy Jones, with teaching him how to accompany a singer, a skill that shaped the rest of his career. That August he was at the marathon Los Angeles session that produced EmArcy's Dinah Jams, with Clifford Brown, Max Roach, Clark Terry and Maynard Ferguson in the room. In 1956 he joined the first civilian quintet Cannonball Adderley put together, with Nat Adderley, Sam Jones and Jimmy Cobb, and stayed two years, recording In the Land of Hi-Fi and Sophisticated Swing for EmArcy. He was freelancing constantly through the same stretch: a session with Art Blakey's Jazz Messengers on October 9 and 11, 1957 that became Bethlehem's Hard Drive, Wilbur Ware's The Chicago Sound for Riverside, and the September 1958 Chicago big-band date that produced James Moody's Last Train from Overbrook. When the Adderley band folded for lack of work, Mance joined Dizzy Gillespie's quintet, once again taking over from Wynton Kelly, and in January 1959 he was at the piano behind Gillespie and Louis Armstrong for a televised "Umbrella Man" on CBS.

Norman Granz heard him on one of those Gillespie sessions and offered him a date of his own. In April 1959, with Ray Brown on bass and Lex Humphries on drums, Mance cut Junior for Verve. The trio format he chose there stayed with him for six decades. What followed was the most concentrated leader run of his life: six albums for Riverside and its Jazzland subsidiary between 1960 and 1963, all produced by Orrin Keepnews, beginning with The Soulful Piano of Junior Mance in October 1960 and including Big Chief!, The Soul of Hollywood with Melba Liston's arrangements, Happy Time with Ron Carter and Mickey Roker, and Junior's Blues. The best-known of them was recorded live on February 22 and 23, 1961 with Larry Gales and Ben Riley: Junior Mance Trio at the Village Vanguard, still the record most listeners reach for first. He was simultaneously the pianist in the Eddie "Lockjaw" Davis/Johnny Griffin quintet, one of the hardest-swinging two-tenor bands of the period, cutting Tough Tenors in November 1960 and a long series of live sets at Minton's Playhouse.

Three albums for Capitol followed in 1964 and 1965, two of them setting his trio against Bob Bain's brass ensemble with Shelly Manne on drums. Then came four years at Atlantic under producer Joel Dorn, the most stylistically restless period of his catalog: Harlem Lullaby put him on harpsichord, I Believe to My Soul surrounded the trio with Arif Mardin's charts and a band including Frank Wess, David "Fathead" Newman, Hubert Laws and Ray Barretto, Live at the Top of the Gate documented the working group, and 1970's With a Lotta Help from My Friends pushed into electric territory with Chuck Rainey, Eric Gale and Billy Cobham. He also kept one foot in the blues he had grown up on, sitting in with Buddy Guy and Junior Wells in December 1969 for Buddy and the Juniors and playing on Aretha Franklin's Soul '69. Hansen House published his instruction book How to Play Blues Piano in June 1967.

From the mid-1970s onward Mance worked at a steadier, less commercially driven pace: Japanese labels for Holy Mama and Live at Sweet Basil, a long duo and trio partnership with bassist Martin Rivera through the 1980s, solo piano records for Canada's Sackville, and a Chiaroscuro association built around the annual Floating Jazz Festival cruises. He toured Japan repeatedly between 1990 and 2009 as part of the rotating all-star piano package "100 Gold Fingers." In 1988 he joined the faculty of the New School for Jazz and Contemporary Music in Greenwich Village and taught there for 23 years, teaching blues, blues ensembles and private piano until he retired in 2011; Brad Mehldau and Larry Goldings both studied with him there. In 2007 he and his wife and manager, Gloria Clayborne Mance, started their own label, JunGlo, launching it with a trio set recorded at Café Loup, the Greenwich Village bistro where he held a Sunday night residency until he stopped playing in spring 2016. A stroke in 2015 and the dementia that followed ended the residency; he cut a last album, For My Fans, It's All About You, in Brooklyn in February 2015. Junior Mance passed away at his New York home on January 17, 2021, at 92.

Mance built everything on the blues, and did it without ever sounding like a revivalist. He came up hearing his father's stride and boogie-woogie, absorbed bebop harmony working next to Gene Ammons and Sonny Stitt, and then spent two years learning from Dinah Washington's book how to leave space for a voice. The result was a style with a left hand that kept a churchy, insistent bottom under everything and a right hand that worked in short, riffing, gospel-inflected phrases rather than long bebop lines. A New York Times critic once described "riffs that prod and poke against the rhythm," which is close to exact. He was a first-call accompanist for exactly that reason, equally at home behind two roaring tenors in the Davis/Griffin quintet, behind Dinah Washington and Etta Jones, and behind Buddy Guy on an acoustic blues date. His playing changed remarkably little across sixty years, and by the 1990s a generation of New School students, Brad Mehldau among them, sought him out specifically to learn how a pianist supports a soloist.