John Haley Sims was born October 29, 1925, in Inglewood, California, to the vaudeville performers Kate Haley and John Sims. His father worked as a tap dancer and taught his son dance steps at home; his brother Ray Sims became a professional trombonist. Sims took up drums and clarinet as a boy, moved to tenor saxophone at thirteen, and built his early conception directly on Lester Young, Ben Webster, and Don Byas. The nickname arrived before the career did: joining Kenny Baker's band at fifteen, he found the music stands decorated with nonsense words, and the one in front of his chair read "Zoot." He dropped out of high school, worked in big bands led by Baker and Bobby Sherwood, and in 1943, at seventeen, joined Benny Goodman's orchestra. In 1944 he replaced Ben Webster in Sid Catlett's quartet and made his recording debut that May for Commodore Records in a sextet led by pianist Joe Bushkin. He served as a corporal in the United States Army Air Forces from 1944 to 1946, then rejoined Goodman.

The job that made his name came in 1947, when Woody Herman built the Second Herd around a saxophone section of three tenors and a baritone. Sims sat in it alongside Stan Getz, Herbie Steward, and Serge Chaloff, with Al Cohn soon taking Steward's chair, and the band recorded Jimmy Giuffre's "Four Brothers" for Columbia on December 27, 1947. The tune gave the section its permanent nickname and gave Sims a reputation he never had to rebuild. The Second Herd's ranks over its short life also took in Gene Ammons, Lou Levy, Oscar Pettiford, Terry Gibbs, and Shelly Manne, and its other hit, "Early Autumn," became one of the defining ballad performances of the late 1940s. Sims stayed until 1949, then moved through a string of bands as the big-band economy collapsed: Buddy Rich's short-lived orchestra, Artie Shaw, another spell with Goodman in 1950, Chubby Jackson, Elliot Lawrence, and a 1953 European tour with Stan Kenton. His own first sides as a leader came in this period, quartet dates cut in Paris in 1950 and for Prestige in 1951 that Prestige later gathered on the LP Quartets (1956).

From 1954 to 1956 Sims worked in Gerry Mulligan's pianoless sextet, heard on Presenting the Gerry Mulligan Sextet (EmArcy, 1956) and Mainstream of Jazz (EmArcy, 1957), where his tenor was paired against Bob Brookmeyer's valve trombone and Mulligan's baritone. When Mulligan assembled the Concert Jazz Band in the spring of 1960, Sims went into that too, a thirteen-piece group whose personnel over its run included Thad Jones, Clark Terry, Phil Woods, and Gene Quill. Verve issued Gerry Mulligan Presents a Concert in Jazz in 1961 and, in 1962, Gerry Mulligan and the Concert Jazz Band on Tour, whose sleeve billed Sims explicitly as guest soloist.

Running underneath all of it was the partnership that defined his working life. Sims and Al Cohn had met in the Herman band and began co-leading a two-tenor quintet in the early 1950s, recording From A to Z for RCA Victor in 1957, Al and Zoot for Coral on March 27, 1957, and You 'n' Me for Mercury in 1960. In January 1959 the quintet took a season at the Half Note, a small club at Hudson and Spring in lower Manhattan, and became the room's signature act; United Artists recorded them there on February 6 and 7, 1959, with Mose Allison on piano, Knobby Totah on bass, and Paul Motian on drums, and issued the results as Jazz Alive! A Night at the Half Note. The two also backed Jack Kerouac on Blues and Haikus (Hanover, 1959), one of the few recordings to put Kerouac's reading against live improvising rather than a written score. Sims's own leader dates piled up in parallel: The Modern Art of Jazz (Dawn, 1956), Zoot! (Riverside, recorded December 13 and 18, 1956, with Nick Travis, George Handy, Wilbur Ware, and Osie Johnson), Tenor Conclave (Prestige, 1957) alongside Cohn, Hank Mobley, and John Coltrane, Down Home (Bethlehem, 1960), Choice (Pacific Jazz, 1961), the live Zoot Sims in Paris (United Artists, recorded 1961), and Waiting Game, cut in London on November 28 and 30, 1966 with an orchestra arranged by Gary McFarland and released by Impulse! in 1967.

In 1962 the State Department sent Benny Goodman's band to the Soviet Union, the first American jazz orchestra to tour there, for thirty performances in six cities over five weeks; Nikita Khrushchev attended the opening night in Moscow, and RCA Victor released the results as Benny Goodman in Moscow. Sims and Phil Woods were in the septet, and Sims left behind the tour's most quoted line when he was asked what playing with Goodman in Russia had been like: every gig with Benny, he said, is like playing in Russia. The 1960s otherwise found him freelancing constantly. He was in the band for Pepper Adams's 1963 Workshop Jazz leader date Pepper Adams Plays the Compositions of Charlie Mingus, issued in 1964, with Thad Jones and Charles McPherson beside him and the whole program drawn from Charles Mingus's book, and he returned for Adams's Encounter!, cut at Nola Penthouse Sound Studios on December 11 and 12, 1968 with Tommy Flanagan, Ron Carter, and Elvin Jones. Into the 1970s he recorded regularly with Bucky Pizzarelli, Joe Venuti, and Jimmy Rowles, cutting Joe & Zoot for Chiaroscuro and Nirvana for Groove Merchant, both in 1974, and turned up outside jazz too, playing a thirty-second tenor solo on Phoebe Snow's "Poetry Man" from her 1974 debut album.

The last decade was the best documented of his career. Sims began recording for Norman Granz's Pablo label in 1975 and appeared on more than twenty Pablo albums, as a leader and as a featured horn behind Count Basie, Sarah Vaughan, and Clark Terry. Zoot Sims and the Gershwin Brothers, recorded at RCA Studios in New York on June 6, 1975, put him in front of Oscar Peterson, Joe Pass, George Mraz, and Grady Tate. Basie & Zoot, a quartet date with Basie, John Heard, and Louie Bellson cut on April 9, 1975, won Basie the 1977 Grammy for Best Jazz Performance by a Soloist at the 19th Grammy Awards. Sims had started doubling on soprano saxophone in 1973, and Granz gave him a full album on the horn: Soprano Sax, recorded over two days in January 1976 at RCA Studios in New York with Ray Bryant, Mraz, and Tate. Hawthorne Nights followed in September 1976, a nine-piece session written and conducted by Bill Holman. Between 1974 and 1983 Sims made six quartet records with Jimmy Rowles, among them If I'm Lucky (1978) and Warm Tenor (1979), and rounded out the Pablo run with Passion Flower: Zoot Sims Plays Duke Ellington (1980), Just Friends with Harry "Sweets" Edison (1980), Blues for Two with Joe Pass (1983), and Quietly There: Zoot Sims Plays Johnny Mandel (1984).

Sims married the journalist Louise Ault in 1970, and by most accounts stopped drinking after years of heavy alcohol use that had damaged his kidneys and liver. His final studio session was a trio date recorded in Sweden in November 1984 with bassist Red Mitchell and guitarist Rune Gustafsson, released in 1985 by Sonet and Pablo as In a Sentimental Mood. He had been ill with cancer for several months when he passed away on the morning of March 23, 1985, at Mount Sinai Hospital in New York, at 59. He is buried in Oak Hill Cemetery in Nyack, New York.

Sims built his sound on Lester Young's light, buoyant tenor conception and then kept it, essentially unaltered, across forty years in which jazz went through bebop, cool, hard bop, modal playing, and free improvisation without ever pulling him off his line. What he offered instead of stylistic change was reliability of a rare kind: a warm, slightly grainy tone, phrasing that landed exactly where the beat wanted it, and, as Scott Yanow put it, a career in which he never played an inappropriate phrase. That made him the ideal foil rather than a competitor, which is why he worked so well opposite Al Cohn, whose sound was close enough to his that listeners often could not tell the two tenors apart, and why he thrived in settings as different as Gerry Mulligan's pianoless sextet, Count Basie's rhythm section, and the four-tenor free-for-all of Tenor Conclave alongside John Coltrane. Adding soprano saxophone in 1973 broadened the palette without changing the approach. His influence runs most directly through the swing-rooted tenor players who came up after him: Harry Allen got one of his first professional breaks subbing for an unavailable Sims on a studio date and later recorded the 1997 tribute album Here's to Zoot.