Egberto Amin Gismonti was born on December 5, 1947, in Carmo, a small town in the interior of Rio de Janeiro state, into a family of musicians. His father, Camilo Amim, was Lebanese and his mother, Ruth, was of Italian descent; AllMusic adds that his grandfather and an uncle led bands. He began on the piano as a small child and studied it for about fifteen years, added flute and clarinet at the Brazilian Conservatory of Music, and took up the guitar in his teens, teaching himself. Because he wanted the guitar to do what a piano does, he had instruments with more than six strings made for him and worked out his own two-handed technique on them. At twenty he turned down a scholarship to study classical music in Vienna in order to work in popular music. In October 1968 his song "O Sonho," which he had arranged for a hundred-piece orchestra, was performed by the group Os Três Morais at TV Globo's third International Song Festival in Rio, and AllMusic reports that it was recorded eighteen times by other artists.

Soon afterward he left for France, where he spent about a year and a half as conductor and orchestrator for the singer Marie Laforêt and became a pupil of the composers Jean Barraqué and Nadia Boulanger. Boulanger urged him to write Brazil's collective experience into his music, and he went home in 1971 to do it. His first LP, Egberto Gismonti (Elenco, 1969), mixed his own songs with a tribute to Wes Montgomery and was cut with the drummer Wilson das Neves and the bassist Sérgio Barroso. Sonho 70 (Polydor, 1970) was produced by Roberto Menescal, and Orfeo Novo (MPS, issued in Germany in 1971) was produced by Joachim Ernst Berendt, with the bassist J.-F. Jenny-Clark and the flutist Bernard Wystraëte. Back in Brazil he made Água e Vinho (Odeon, 1972) with the lyricist Geraldo Carneiro, which holds two of his best-known songs, "Ano Zero" and "Água e Vinho," and then Academia de Danças (EMI/Odeon, 1974), the record AllMusic names as the turning point toward instrumental music and says earned a gold record in Brazil. Between 1972 and 1991, by AllMusic's count, he made nineteen albums for EMI/Odeon.

In 1974 he accepted an invitation to a festival in Berlin and asked Hermeto Pascoal and Naná Vasconcelos to appear with him. There he met Manfred Eicher, the head of ECM Records, and a letter from the label followed in 1975 inviting him to record; according to AllMusic he did not answer until the end of 1976. He had meant to record with his Brazilian band, but the cost of taking them abroad ruled that out, and in Norway he enlisted Vasconcelos instead. Dança das Cabeças was recorded in Oslo in November 1976 and released in 1977 as his ECM debut. AllMusic says it was honored as a pop record in England, a folk record in the United States and a classical record in Germany; English Wikipedia adds that Stereo Review nominated it for album of the year and that it won Germany's Großer Deutscher Schallplattenpreis for 1977.

After that record he went into the upper Xingu region of the Amazon basin and spent about a month with the Yawalapiti, having played his flute for two weeks until their chief, Sapaim, invited him in, AllMusic recounts. Sol do Meio Dia (recorded November 1977, released 1978) is dedicated to the Xingu peoples and brings Vasconcelos, Ralph Towner on twelve-string guitar, Collin Walcott on tabla and Jan Garbarek on soprano saxophone onto some of its tracks. Solo (recorded November 1978, released 1979) is a solo set for piano, eight-string guitar and percussion that AllMusic says sold 100,000 copies in the United States. In 1978 he founded his own label, Carmo, through which he later bought back his early recordings; Portuguese Wikipedia notes that this makes him one of the few Brazilian composers who own their own catalog. In June and November 1979 he recorded Magico and Folk Songs in Oslo with the bassist Charlie Haden and Garbarek, a trio that toured Europe in 1981; one of those concerts, recorded in Munich in April 1981, appeared only in 2012 as Magico: Carta de Amor. The same year he released the double album Sanfona, a studio disc with his quartet Academia de Danças (the saxophonist and flutist Mauro Senise, the bassist Zeca Assumpção, and the drummer Nenê) and a solo concert disc.

Duas Vozes, a second duo record with Vasconcelos, was made in Oslo in June 1984 and released in 1985. Dança dos Escravos (1989) is a solo album of guitar pieces played on six-, ten-, twelve- and fourteen-string instruments. In 1990 he toured the United States with a group that included the cellist Jaques Morelenbaum, the saxophonist and flutist Nivaldo Ornelas and the keyboardist Edu Mello e Souza, and with Morelenbaum, the guitarist Nando Carneiro and Zeca Assumpção he recorded Infância (ECM, 1991) and Música de Sobrevivência (ECM, 1993), the second inspired by the poet Manoel de Barros. Meeting Point (ECM, 1997), which AllMusic says was recorded in 1995, features him as pianist and composer with the Lithuanian State Symphony Orchestra, and ZigZag (1996) is a trio record with Carneiro and Assumpção. In Montreal (ECM, 2001) is a live duo with Haden. Saudações (ECM, 2009) is a double album: the seven-part suite Sertões Veredas: Tributo à Miscigenação, recorded with the Cuban string orchestra Camerata Romeu, and a second disc of guitar duets with his son Alexandre Gismonti. He has also written for film, and AllMusic lists soundtrack work from 1969 and 1971. Portuguese Wikipedia reports that Rolling Stone Brasil named him one of the thirty great Brazilian guitar and violão icons in 2012, and he was still performing in 2025, when he appeared in Santiago, Chile, with Morelenbaum and Daniel Murray.

Gismonti's music spans jazz, Brazilian art music and popular song, and contemporary classical writing. ECM describes his work as standing at the crossroads of Brazil's folk tradition and the world of classical music, in a way that echoes Heitor Villa-Lobos, and adds that he is also a masterful improviser. AllMusic lists jazz first among his genres, with classical, international and new age after it, and names Brazilian jazz first among his styles, ahead of global jazz, samba, Brazilian folk, Latin jazz and chamber music. English Wikipedia opens by calling him a Brazilian composer, guitarist and pianist, and AllMusic reports that Dança das Cabeças was honored as a pop record in England, a folk record in the United States and a classical record in Germany. The jazz connection is real and well documented: his ECM trio with Charlie Haden and Jan Garbarek was an improvising group, English Wikipedia files his ECM albums, including the duos with Naná Vasconcelos, under jazz, and in the mid-1970s he played on records by Cal Tjader, Airto Moreira and Paul Horn. But his own compositions draw on the choro, samba, frevo, baião and forró of Brazil, on the music of the Xingu peoples, on Villa-Lobos, Stravinsky and Bach, and on what he learned from Boulanger and Barraqué, and a large share of his catalog is orchestral, chamber or solo writing rather than jazz. AllMusic observes that jazz plays a significant role among the musical languages he commands, alongside Brazilian popular and folk forms and a classical training. As a guitarist he is known for treating the fretboard like a keyboard, so that one instrument can sound like two players, and for his custom ten-, twelve- and fourteen-string guitars. Portuguese Wikipedia lists Esperanza Spalding, Hamilton de Holanda and André Mehmari among the musicians who have recorded his pieces, and de Holanda and Mehmari devoted a whole album to the music of Gismonti and Pascoal.