Jim McNeely was born in Chicago on May 18, 1949 into a musical household: his mother sang in the church choir, his father played piano by ear and only in G flat, and his brother went on to play bass around Chicago. He started piano at six and at eight began studying with Bruno Michelotti, who taught him theory alongside the instrument, which is where his lifelong interest in how music is put together began. He picked Notre Dame High School for Boys partly because it had a big band, the Melodons, directed by Rev. George Wiskirchen, and he was writing arrangements for it by the age of sixteen. He chose the University of Illinois for much the same reason, its band under John Garvey, and studied theory and composition there with Ed London and Morgan Powell. The degree took him eight years, from 1967 to 1975, and the years around it were spent on the Champaign-Urbana scene alongside Cecil Bridgewater and the saxophonist Ron Dewar, in jam sessions with visiting New York bands at a club called Ruby Gulch, and in six months of six-nights-a-week work with a country band. While still a teenager he turned up in DownBeat twice, once as a young composer worth watching and once as the author of an Ornette Coleman transcription.

He moved to New York in 1975 with a composition degree and the intention of working as a jazz pianist. The first records came quickly: two dates with the trumpeter Ted Curson in 1976, and his own debut for SteepleChase, Rain's Dance, cut in October of that year with Larry Schneider, Mike Richmond, Bob Merigliano and Sam Jacobs. The gig that changed everything arrived in 1978, when he took the piano chair in the Thad Jones/Mel Lewis Orchestra for its Monday nights at the Village Vanguard. He stayed six years with that band and its successor, Mel Lewis and the Jazz Orchestra, and the transition from pianist to composer began almost immediately after it: Thad Jones left for Copenhagen in 1979, Mel Lewis brought in Bob Brookmeyer as musical director, and Brookmeyer told him to write for the band. By McNeely's own account the first chart was a disaster, the second a little better, and the third, "Blue Note", good enough for Lewis to record. Brookmeyer had found the successor he was looking for, and McNeely later said he was lucky the older man had seen something in him and pushed him to develop it.

Two long tenures in working small groups ran alongside the big-band writing. In 1981 he began four years as pianist and composer with the Stan Getz Quartet, a run documented on Pure Getz and Blue Skies for Concord, on Live in Paris, and on the 1983 tour that paired Getz with Chet Baker and produced Line for Lyons and The Stockholm Concert. From 1990 to 1995 he held the piano chair in the Phil Woods Quintet. He wrote steadily for both leaders, and the Woods association closed with the band recording an entire program of his tunes as Plays the Music of Jim McNeely. In the same years he turned up on other people's records in most formats from duo upward: David Liebman's Homage to John Coltrane and Time Line, Bobby Watson's Advance, Art Farmer and Slide Hampton's In Concert, Nick Brignola's Northern Lights, and Rufus Reid's trio date Seven Minds, cut in November 1984 with Terri Lyne Carrington on drums.

Europe made him a big-band composer. Brookmeyer took him and Lewis to Cologne in 1983 as a soloist on a WDR Big Band project, he began writing for that band, and the association lasted eleven years; he called it his real composer's workshop. It produced East Coast Blow Out, recorded at the WDR studios in September 1989 with John Scofield, Marc Johnson and Adam Nussbaum out in front of the orchestra, and the record is generally treated as the point at which his writing arrived. Work with UMO in Helsinki, the Stockholm Jazz Orchestra, the Metropole Orkest and the Swiss Jazz Orchestra followed, along with two Stockholm albums, Jigsaw in 1991 and Sound Bites in 1997, and the Paul Klee suite he wrote for the Bern orchestra in 2005. In 1998 he became chief conductor of the Danish Radio Big Band in Copenhagen, a post he held into the early 2000s and which yielded four albums: a Gershwin program, Nice Work; an Armstrong salute with the New Orleans trumpeter Leroy Jones, The Power and the Glory; a big-band reading of Bill Evans compositions, Play Bill Evans; and Dedication Suite, taped in November 2002 and released four years later. He returned to Copenhagen in 2013 to arrange and conduct a record for the singer Judy Niemack.

Back in New York, he rejoined the Vanguard Jazz Orchestra, the same band under its third name, as pianist and composer in residence, and stayed in that role for the rest of his life. He wrote two full programs for it, Lickety Split in 1997 and Up from the Skies in 2006, and both were nominated for Best Large Jazz Ensemble Album, as was the band's Monday Night Live at the Village Vanguard, which won the award at the 51st Grammy Awards in 2009 and gave him the one Grammy of his twelve nominations. He also wrote extensively for the Carnegie Hall Jazz Band, arranged "Black Holes" for Renee Rosnes and the Danish Radio Big Band, and led his own ten-piece band on Group Therapy, made in New York in June 2000. The Frankfurt Radio Big Band became the longest of his European relationships: artist in residence from August 2008, chief conductor from August 2011, composer in residence from the 2022/23 season, and after a farewell concert in 2024 the band's first Conductor Laureate. He made A Single Sky there with Dave Douglas in 2009, Quest for Freedom with David Liebman and Richie Beirach the same year, Barefoot Dances and Other Visions, whose 2019 nomination was his last, and Rituals, an Alte Oper commission built on Stravinsky's The Rite of Spring with Chris Potter as soloist. The Jazz Orchestra of the Concertgebouw devoted a whole album, Threnody, to his writing in 2022.

Teaching mattered to him as much as the writing. He was professor emeritus in jazz composition at the Manhattan School of Music, where he had joined the Jazz Arts faculty in 2008 and where Miho Hazama studied with him from 2010; he also held positions at William Paterson University and New York University, and was involved with the BMI Jazz Composers Workshop for twenty-four years, sixteen of them as its musical director. He and his wife Marie had retired to Owls Head, Maine when he was diagnosed with bile duct cancer, and the couple returned to New York for treatment. On September 10, 2025 he was in the audience at the DiMenna Center for a retrospective concert of his compositions played by an eighteen-piece band, with Rufus Reid as master of ceremonies. He passed away in New York on September 26, 2025, at seventy-six, survived by Marie, his children Clare, Grace and Peter, a daughter-in-law, a grandson and two siblings. Two records have appeared since: Trilogue + 15, his Albert Mangelsdorff arrangements taped in concert at the Alte Oper in 2018, and Expeditions, a suite of twelve pieces he completed and recorded live with the Frankfurt band on June 13, 2024, each one written as a feature for an individual player, released in August 2026.

McNeely came to New York as a pianist whose vocabulary was built out of the 1960s, McCoy Tyner and Herbie Hancock and Chick Corea, and the thing that made him valuable was that he could take that harmonic equipment into a band led by someone twenty years older and make it fit, which is how a young firebrand ended up holding multi-year chairs with Stan Getz and Phil Woods. The same harmonic hearing is what he put into the writing. His charts characteristically run quick saxophone lines over skittering, sometimes ominous syncopated bass figures, with the lyrical weight carried by sustained brass shapes placed against the beat rather than on it, and while the results are complicated to listen to they are not hard to play: he wrote what each section could actually execute, and an eight-minute piece unfolds by division rather than by assembly. That combination of ambition and practicality is why the European radio orchestras kept commissioning him and why big-band composers treat East Coast Blow Out as a source text. The lineage is explicit and documented rather than inferred: Thad Jones and Mel Lewis gave him the bandstand, Bob Brookmeyer gave him the assignment and the standard, and he passed both on through the Vanguard book, the BMI workshop and a Manhattan School of Music classroom to a generation that includes the composer who succeeded him but one in Copenhagen. The New York Times called his writing exhilarating and DownBeat called it eloquent enough to be profound; after his death Maria Schneider said that he had left the world a tremendous amount of music, and that she and others would go on discovering it, studying it, playing it and marvelling at it.