Hermeto Pascoal Oliveira da Costa was born on June 22, 1936, in Olho d'Água das Flores, in the northeastern Brazilian state of Alagoas, in a rural area that had no electricity at the time. Because he was born with albinism he could not work the fields with the rest of his family, and he spent his days learning the accordion from his father. He and his brother José Neto both looked up to the baião accordionist Luiz Gonzaga. A self-taught child prodigy, he took up the flute at seven, scat sang, whistled, and imitated birdcalls, and by eleven he was playing in groups with his father and brother while the family moved between Recife and Caruaru. With his brother and the accordionist Sivuca, who also had albinism, he formed a short-lived accordion trio, O Mundo em Chamas.

He taught himself piano, woodwinds, and percussion, and at the end of the 1950s moved south to make a living in Rio de Janeiro and São Paulo. In 1960 he picked up the saxophone and formed the group Som Quatro, which made a Continental LP in 1964. That year he also joined the Sambrasa Trio with Airto Moreira and the bassist Humberto Clayber; the trio left one album, Em Som Maior (1965). He then joined Trio Novo, with Airto, the guitarist Heraldo do Monte, and the bassist Theo de Barros, which became Quarteto Novo when he arrived on flute and piano. The group backed Edu Lobo on "Ponteio," which won best song at the third Festival de Música Popular Brasileira in 1967, and recorded its only album, Quarteto Novo (Odeon, 1967), before disbanding in 1969. The record is credited with bringing the baião of the Northeast to a national audience and with launching the careers of both Pascoal and Airto.

In 1969 Flora Purim and Airto invited him to the United States, where he recorded two Buddah LPs with them as composer, arranger, and instrumentalist. His own debut, Hermeto, followed in 1970 on Cobblestone, recorded in New York with Airto, Flora Purim, Ron Carter on bass, and a studio ensemble of brass, strings, and woodwinds that included Hubert Laws and Joe Farrell. That year he also played flute on "Xibaba" on Donald Byrd's Electric Byrd (recorded May 15, 1970), took a flute solo on Antonio Carlos Jobim's Tide, and played flute, guitar, and bass on Duke Pearson's It Could Only Happen with You, which also carries his composition "Hermeto." The breakthrough abroad came through Miles Davis: three of his pieces, "Little Church," "Nem Um Talvez," and "Selim," were recorded in New York on June 3 and 4, 1970, with Pascoal playing drums, electric piano, whistling, and voice across them, and were released on Davis's double album Live-Evil in November 1971. Davis reportedly called him the most impressive musician in the world.

Back in Brazil he made A Música Livre de Hermeto Pascoal (1973), then returned to the United States in 1976 to record Slaves Mass for Warner Bros., issued in 1977, with Purim, Airto, Ron Carter, the trombonist Raul de Souza, and the bassist Alphonso Johnson. Pascoal plays piano, keyboards, clavinet, melodica, soprano saxophone, flutes, and guitars on it, and live pigs are credited on the title piece. From the late 1970s he mostly led his own band, whose members over the years included bassist Itiberê Zwarg, pianist Jovino Santos Neto, and percussionists Nenê, Pernambuco, and Zabelê. It recorded Zabumbê-bum-á (1979) and played the Montreux Jazz Festival in 1979, a set released as a double album. He also appeared at Montreux with Elis Regina, whose live album from the festival, released in 1982, features him on three tracks. The group's recordings continued with Cérebro Magnético (1980), Hermeto Pascoal & Grupo (1982), Lagoa da Canoa, Município de Arapiraca (1984), Brasil Universo, and Só Não Toca Quem Não Quer (1987), and at the end of the 1980s he made a solo piano album, Hermeto Solo: Por Diferentes Caminhos.

Between 1996 and 1997 he worked on Calendário do Som, a book of pieces with one for every day of the year, including February 29, so that every birthday would have a song; it was published by Senac. He lived for many years in the Jabour neighborhood of Bangu in Rio de Janeiro, composing, rehearsing, and hosting musicians from around the world. He recorded as a duo with his second wife, the singer Aline Morena (Chimarrão com Rapadura, 2006, and Bodas de Latão, 2010), and in 2013 made The Monash Sessions with the Sir Zelman Cowen School of Music at Monash University in Australia. Far Out Recordings issued two archive sets, Viajando com o Som (a 1976 studio session by his group Vice Versa, released in 2017) and Planetário da Gávea (2022). In 2017 he released the double album No Mundo dos Sons and, with a big band, Natureza Universal, which won the Latin Grammy for best Latin jazz album in 2018. A year later Hermeto Pascoal e Sua Visão Original do Forró won the Latin Grammy for best Portuguese language roots album, and in 2024 Pra Você, Ilza, a tribute to his first wife, Ilza da Silva, to whom he was married from 1954 until her death in 2000, won the Latin Grammy for best Latin jazz album. It was the last album released in his lifetime.

Pascoal passed away of multiple organ failure in Rio de Janeiro on September 13, 2025, at 89. He had six children with Ilza. Brazilian audiences knew him as O Bruxo, the Sorcerer.

Pascoal was known above all for orchestration and improvisation, and for a way of making music out of whatever was at hand: besides keyboards, accordions, melodica, saxophones, guitars, flutes, and his own voice, he played teapots, children's toys, and animals, and used nature as a basis for his compositions. In his Música da Lagoa the musicians burble water and play glass bottles and flutes while immersed in a lagoon, and a 1999 Brazilian television broadcast showed him soloing by singing into a cup with his mouth half submerged. His foundation was the rural folk music of the Northeast, the baião and forró of Luiz Gonzaga's tradition, which he set beside samba and the harmonic and improvisational language of jazz, a mix that placed him in Miles Davis's circle and made him a fixture at jazz festivals. By Discogs' count he composed more than two thousand pieces, and they include works for symphony orchestra as well as for his own groups. The Brazilian scholar Luiz Costa-Lima Neto wrote a book-length study of his group's work from 1981 to 1993 (Pendragon Press, 2015). Younger musicians have kept playing his music, among them Mike Marshall and Jovino Santos Neto on Serenata: The Music of Hermeto Pascoal (2003), the Israeli flutist Mattan Klein, whose 2022 album The Long Run is a tribute to him, Diego Urcola, who dedicated one of the nine originals on his album of musician dedications to Pascoal, Hamilton de Holanda, who recorded a tribute album of Pascoal and Egberto Gismonti pieces with the pianist André Mehmari, and the harmonica player Gabriel Grossi, whose 2026 tribute Hermeto Universal was made with Laurent Coulondre and, on bass, Michael League.