Kenneth Vincent John Wheeler was born in Toronto on January 14, 1930, picked up the cornet at twelve, and turned toward jazz in his mid-teens. He spent a single year, 1950, studying composition at the Royal Conservatory of Music in Toronto, then left Canada in 1952 for Britain, where he stayed for the remaining sixty-two years of his life. He worked his way into the London scene through the bands of Tommy Whittle, Tubby Hayes, and Ronnie Scott; his earliest surviving commercial credits are Tommy Whittle Orchestra sides cut for Esquire in 1956. In the late 1950s he played in Buddy Featherstonhaugh's quintet alongside the Scottish tenor player Bobby Wellins.

From 1959 to 1965 Wheeler held a trumpet chair in John Dankworth's orchestra, the steadiest employment of his early career and the setting in which he began writing seriously for large ensemble. He studied composition privately with Richard Rodney Bennett in 1962-63 and with the Kenton arranger Bill Russo in 1963-64, and recorded with Dankworth on What the Dickens! (1963) and The Zodiac Variations (1965). In a 1961 interview with Kitty Grime, his fellow Dankworth trumpeter Dickie Hawdon singled Wheeler out as the one British-based player who did not copy his ideas off records. In 1965 Wheeler also turned up in the one-off Animals' Big Band at the fifth British Jazz and Blues Festival in Richmond, sharing a trumpet section with Ian Carr.

Two things happened at once in the late 1960s. Wheeler made his first album under his own name, Windmill Tilter, a nine-part suite on Cervantes's Don Quixote recorded in March 1968 with the Dankworth orchestra and issued on Fontana in 1969; it carried John McLaughlin's last British studio work before he left for New York and the first recorded appearance of bassist Dave Holland. At the same time Wheeler became one of the few players moving freely between the London mainstream and the free improvisation scene forming around John Stevens and Evan Parker. He is on the Spontaneous Music Ensemble's Karyobin (1968), Tony Oxley's The Baptised Traveller (1969), Mike Westbrook's Marching Song (1969), and from 1973 the Globe Unity Orchestra, and he held a chair in Ronnie Scott's nine-piece band from 1971 to 1975. His second leader date, Song for Someone, recorded January 10 and 11, 1973 at Olympic Sound Studios and released on Derek Bailey and Evan Parker's Incus label, set his orchestral writing against free passages from Bailey, Parker, and Oxley. He was also the trumpeter in the Anthony Braxton Quartet from 1971 to 1976, appearing on New York, Fall 1974, Five Pieces 1975, and Creative Orchestra Music 1976.

Manfred Eicher signed Wheeler to ECM in 1975, beginning the association that made his international reputation. Gnu High, cut in June 1975 at Generation Sound Studios in New York with Keith Jarrett, Dave Holland, and Jack DeJohnette, is three long pieces and one of the very few records on which Jarrett plays as a sideman. Deer Wan followed in July 1977 at Talent Studio in Oslo with Jan Garbarek, John Abercrombie, and Ralph Towner added to the Holland/DeJohnette rhythm section, then Around 6 (August 1979) with Evan Parker and Eje Thelin, and Double, Double You (May 1983, the Power Station in New York) with Michael Brecker. Alongside the ECM leader dates Wheeler co-founded Azimuth in 1977, a trio with pianist John Taylor and singer Norma Winstone that recorded five albums for the label between 1977 and 1995 and lasted until 2000. His one Canadian leader date of the period, a quintet session with Art Ellefson cut live in Toronto in February 1976 for Radio Canada International, has circulated under three different names: Kenny Wheeler Quintet, Ensemble Fusionaire, and 1976.

January and February 1990 produced the two records most often named as his peak. Music for Large & Small Ensembles (ECM 1415/16), taped at CTS in London and Rainbow Studio in Oslo, contains "The Sweet Time Suite," his most ambitious extended big-band writing since Windmill Tilter, plus "Sea Lady" and a set of duets and trios; The Widow in the Window (ECM 1417) is the quintet from the same sessions with Peter Erskine on drums. Between them came Soul Note dates under the Kenny Wheeler Quintet billing, Flutter By, Butterfly (recorded May 1987, home of his most covered tune, "Everybody's Song But My Own") and All the More (recorded 1993), and the big-band record Kayak (May 1992, Ah Um). In February 1996 he made Angel Song for ECM with a drummerless quartet of Lee Konitz, Dave Holland, and Bill Frisell, the album that drew the widest critical praise of his career, and in 1997-98 recorded A Long Time Ago, a brass-ensemble score produced by Evan Parker.

Wheeler moved to the Italian label CAM Jazz in the 2000s and recorded steadily there into his eighties: the duo Where Do We Go from Here? with John Taylor (February 2004), What Now? with Chris Potter and Holland (June 2004), It Takes Two! (July 2005), Other People with the Hugo Wolf Quartett (October 2005), One of Many with Taylor and Steve Swallow (July 2006), the sextet date Six for Six (April 2008), and The Long Waiting (September 2011), a Kenny Wheeler Big Band record conducted by Pete Churchill. He was appointed an Officer of the Order of Canada in 2007, was made an honorary member of the Royal Academy of Music, and served as patron of the Academy's junior jazz course. His last studio session, Songs for Quintet, was recorded at Abbey Road in December 2013 and issued by ECM in January 2015, timed to what would have been his eighty-fifth birthday. Wheeler passed away at a London nursing home on September 18, 2014, at 84, after a short period of frail health, survived by his wife Doreen and his children Mark and Louanne. On January 20, 2015, Waltham Forest Council put a blue plaque on his old house at 141 Wallwood Road, Leytonstone.

Wheeler's sound is one of the most immediately identifiable in postwar jazz: a wide, unforced flugelhorn tone with an unusually high and secure upper register, and a line built out of large intervallic leaps rather than the scalar bebop vocabulary he came up through. As a trumpet player he took his models from Miles Davis, Clifford Brown, and Art Farmer; as a writer, from Duke Ellington, Gil Evans, Stan Kenton, and Hindemith. He described the two halves of his working life as feeding each other, saying that free playing loosened his conventional playing while the conventional playing gave shape to his free soloing, and he was open about preferring music with a melancholy cast. He wrote more than a hundred pieces, several of which entered the general repertoire, among them "Everybody's Song But My Own," "Kind Folk," "Gentle Piece," and "The Sweet Time Suite," and he was equally trusted as an arranger for a quartet or a seventeen-piece band. His reticence was proverbial: he spent six decades as one of the most sought-after horn players in Europe while remaining, by the account of nearly everyone who worked with him, almost impossible to get to talk about it.