Clark Virgil Terry Jr. was born December 14, 1920, in St. Louis, Missouri, to Clark Virgil Terry Sr. and Mary Terry. He attended Vashon High School, took up the valve trombone before switching to trumpet, and broke into St. Louis's active club scene in the early 1940s, where he gave informal early guidance to a teenage neighborhood horn player named Miles Davis. During World War II, Terry served as a bandsman in the United States Navy, playing from 1941 to 1945 in the all-star Navy band based at Naval Station Great Lakes in Illinois, one of the first Black musicians to serve in a Navy band. After his discharge he joined bandleader Charlie Barnet's orchestra in 1947.

Terry's national reputation was built through consecutive stints inside two of the era's defining big bands. He played in the orchestra and small groups of Count Basie from 1948 to 1951, a period that included Basie's economically driven downsizing to an octet; a 1950 photograph from that stretch shows him alongside Charlie Rouse, Freddie Green, Buddy DeFranco, Jimmy Lewis, and Gus Johnson. It was also during frequent visits to Seattle with the Count Basie Sextet that Terry began mentoring a teenage Quincy Jones. In 1951, Duke Ellington, by Terry's own account in his autobiography, quietly recruited him away from Basie, and Terry remained with the Ellington Orchestra through 1959. He became one of its most valued soloists, featured across many of Ellington's extended suites, including 1957's Such Sweet Thunder, and increasingly specialized on flugelhorn, helping establish the horn as a serious modern-jazz voice years before it became common.

Terry left Ellington in 1959 to join Quincy Jones's touring orchestra for Harold Arlen's musical Free and Easy in Europe. When the production folded, he accepted a staff position with NBC in 1960, and in 1962 became a member of the Tonight Show Band, first under Skitch Henderson and later Doc Severinsen, remaining until 1972. He was the first African American musician to hold a permanent chair in a house band on a major U.S. television network, a role he later described as carrying constant pressure to be flawless: "We had to be models, because I knew we were in a test." It was during these NBC years that his "mumbling" scat-singing style, a good-humored satire of unintelligible old blues shouters, developed into a signature, eventually giving its name to his 1966 Mainstream album Mumbles.

Terry sustained a substantial leader career alongside his sideman and studio work. He debuted as a leader with Clark Terry (1955, EmArcy) and, across a run of Riverside albums, recorded Serenade to a Bus Seat and Duke With a Difference (both 1957), In Orbit (1958, co-starring Thelonious Monk), and Top and Bottom Brass (1959). He cut the septet date Color Changes for Candid in 1961, and at Impulse! recorded The Happy Horns of Clark Terry (1964) and the Chico O'Farrill-arranged Afro-Cuban date Spanish Rice (1966). In the early-to-mid 1960s he co-led a well-received quintet with valve trombonist Bob Brookmeyer, documented on The Power of Positive Swinging (1965) among other albums. He was known for two distinct technical feats: circular breathing, which let him sustain phrases without audibly pausing for air, and an ambidextrous "dialogue" technique in which he played trumpet and flugelhorn at once, one horn in each hand.

Terry remained a visible bandleader and educator through his later decades. He formed his own big band, billed as the Big B-A-D Band, around 1970, and recorded extensively for Norman Granz's Pablo label in the mid-to-late 1970s and into the 1980s, frequently paired with Oscar Peterson on albums including Oscar Peterson & Clark Terry (1975), Ain't Misbehavin' (1979), and Memories of Duke (1980). Education became his abiding cause: prompted early on by pianist Billy Taylor, he and bassist Milt Hinton bought instruments for aspiring young players, planting the seed that grew into Harlem's Jazzmobile program, and he went on to compose more than two hundred original tunes, publish instructional books on circular breathing and jazz trumpet technique, and mentor generations of musicians including Wynton Marsalis, Pat Metheny, Dianne Reeves, and Terri Lyne Carrington. He was named a National Endowment for the Arts Jazz Master in 1991 and received a Grammy Lifetime Achievement Award in 2010.

Terry kept performing and teaching into his 90s even as diabetes progressively cost him his eyesight and, eventually, both legs. His final years, including his mentorship of blind pianist Justin Kauflin, were the subject of the 2014 documentary Keep on Keepin' On. His memoir, Clark: The Autobiography of Clark Terry, appeared in 2011 with a preface by Quincy Jones. Clark Terry passed away on February 21, 2015, in Pine Bluff, Arkansas, at age 94, after an extended battle with diabetes.

Terry's playing was instantly identifiable: a bright, buoyant tone and an unfailingly good-humored sense of swing that made him equally comfortable inside a swing-era orchestra, a bebop small group, or a comedy bit built around his own "Mumbles" scat vocals. He was among the first jazz musicians to make the flugelhorn a primary solo voice rather than an occasional coloristic double, and his technical command, especially his circular breathing and simultaneous two-horn "dialogues," was without close precedent. Beyond his own recordings, his influence ran directly through the musicians he personally shaped: he gave Miles Davis informal early guidance in St. Louis and later mentored Quincy Jones as a teenager, and both men credited him throughout their careers. The Penguin Guide to Jazz Recordings noted that Terry appears on more of its listed recordings than any other artist, a reflection of a session career historians estimate at more than 900 recordings across roughly seven decades.