Pascoal comes from a remote corner of northeastern Brazil, an area that lacked electricity at the time he was born. He learned the accordion from his father and practised for hours indoors as, being albino, he was incapable of working in the fields with the rest of his family.
Hermeto's career began in 1964 with appearances on several Brazilian recordings alongside relatively unknown groups. These now-classic albums and the musicians involved (Edu Lobo, Elis Regina, Cesar Camargo Mariano) established widely influential new directions in post-bossa Brazilian jazz.
In 1966, he played in the Sambrasa Trio, with Airto Moreira and Humberto Clayber; they released only one album, Em Som Maior. Then he joined Trio Novo (Airto Moreira, Heraldo do Monte, Theo de Barros) and in 1967 the group, renamed Quarteto Novo, released an album that launched the careers of Pascoal and Moreira. Pascoal would then go on to join the multi-faceted group Brazilian Octopus.
Pascoal initially caught the international public's attention with an appearance on Miles Davis's 1971 album Live-Evil, which featured him on three pieces, which he also composed. Davis said that Pascoal was "the most impressive musician in the world". Later collaborations involved fellow Brazilian musicians Airto Moreira and Flora Purim. From the late 1970s onward he has mostly led his own groups, playing at many prestigious venues, such as the Montreux Jazz Festival in 1979. Other members of the group have included bassist Itibere Zwarg, pianist Jovino Santos-Neto and percussionists Nene, Pernambuco and Zabele.
Known as o Bruxo (the Sorcerer), Pascoal often makes music with unconventional objects such as teapots, children's toys, and animals, as well as keyboards, button accordion, melodica, saxophone, guitar, flute, voice, various brass and folkloric instruments. Perhaps because he grew up in the countryside, he uses nature as a basis for his compositions, as in his Música da Lagoa, in which the musicians burble water and play flutes while immersed in a lagoon: a Brazilian television broadcast from 1999 showed him soloing at one point by singing into a cup with his mouth partially submerged in water. Folk music from rural Brazil is another important influence in his work.
Between 1996 and 1997, Pascoal worked on a book project called Calendário do Som, which contains a song for every day of the year, including 29 February, so that everyone would have a song for his or her birthday.
Hermeto was married to Ilza da Silva, to whom he composed many themes, from 1954 until her passing in 2000. They had six children, Jorge, Fabio, Flávia, Fátima, Fabiula and Flávio, along many grandchildren. He remarried to Aline Morena from 2003 until 2016, while living in Curitiba, Paraná, Brazil. He has since returned to the Jabour neighborhood in Bangu, Rio, where he spent much of his time living, composing, rehearsing and hosting musicians from all over the world.