Sérgio Santos Mendes was born on February 11, 1941, in Niterói, across Guanabara Bay from Rio de Janeiro. As he related in the 2020 documentary Sergio Mendes in the Key of Joy, he wore a cast for three years as a child because of osteomyelitis; his father was a doctor, and Mendes was one of the first people in Brazil to be given penicillin. He studied classical music at the local conservatory in the hope of becoming a concert pianist, but his interest moved to jazz, and by the late 1950s he was playing in nightclubs just as bossa nova, a jazz-inflected offshoot of samba, was emerging.

He played with Antonio Carlos Jobim, whom he regarded as a mentor, and with the American jazz musicians who came through Brazil; Variety's obituary names Charlie Byrd, Stan Getz, Dizzy Gillespie and Herbie Mann among them. His own group, the Sexteto Bossa Rio, made its first album in 1961, the instrumental Dance Moderno (Philips), which set Brazilian tunes beside Cole Porter's "Love for Sale" and "What Is This Thing Called Love?", Duke Ellington's "Satin Doll" and Horace Silver's "Nica's Dream." In 1962 Mendes came to New York for the bossa nova festival at Carnegie Hall, which he has described as his first visit to the United States, and the sextet played Birdland on a double bill with Cannonball Adderley. Adderley invited him to record, and the Bossa Rio musicians backed the saxophonist on Cannonball's Bossa Nova (made in New York in 1962 and issued by Riverside in 1963), with Mendes at the piano and his tune "Groovy Samba" on the program. The same year he played piano on two tracks of Herbie Mann's Do the Bossa Nova with Herbie Mann (Atlantic), recorded in Rio de Janeiro.

Mendes moved to the United States in 1964. As Sergio Mendes & Brasil '65 and the Sergio Mendes Trio he recorded for Atlantic and Capitol, among them the Atlantic albums In Person at El Matador and The Swinger from Rio, and, according to Variety, did session work with American jazz players such as Art Farmer. The Atlantic jazz albums sold poorly. Richard Adler, who had helped him form Brasil '65, proposed that the group sing in English as well as Portuguese and add two American women singers who could manage both languages, and he arranged an audition for Herb Alpert and Jerry Moss, the founders of A&M Records. They signed the new group, named Brasil '66, and Atlantic's Ahmet Ertegun released Mendes from his Atlantic jazz contract.

What followed was a pop career, and a very large one. Alpert produced the A&M albums and took the group on tour with him. Their first single, "Mas que nada," a song by Jorge Ben, reached No. 47 on the Billboard Hot 100 and No. 4 on the Easy Listening chart in 1966, and the album Herb Alpert Presents Sergio Mendes & Brasil '66 went platinum and was inducted into the Grammy Hall of Fame in 2011. The original Brasil '66 was Mendes on piano, vocalists Lani Hall and Bibi Vogel, Bob Matthews on bass, José Soares on percussion and João Palma on drums, with John Pisano on guitar. On Look Around, Dave Grusin and Dick Hazard wrote orchestrations; its single "The Look of Love," which the group performed on the April 1968 Academy Awards telecast, reached No. 4 on the Hot 100 and No. 2 on the adult contemporary chart, overshadowing Dusty Springfield's version from the film Casino Royale. "The Fool on the Hill" followed to No. 6 (and No. 1 on adult contemporary) and "Scarborough Fair" to No. 16. Mendes played the White House for Lyndon Johnson and Richard Nixon, and the group appeared at Expo '70 in Osaka in June 1970.

He changed the lineup often. Karen Philipp took over the second vocal chair from Janis Hansen, who had replaced Vogel; percussionists Dom Um Romão and Rubens Bassini, drummer Claudio Slon, bassist Sebastião Neto and guitarist Oscar Castro-Neves gave the group a more orchestral sound, and by 1971 it was billed as Brasil '77. Lani Hall left in the early 1970s for a solo career and married Alpert, and Gracinha Leporace, whom Mendes later married, performed with him from the early 1970s. His American career stalled in the middle of the decade, though he stayed popular in South America and Japan. After two albums for Bell in 1973 and 1974 he recorded for Elektra from 1975, including Brasil '88 (1978), and worked with soul writers such as Stevie Wonder, who wrote his minor hit "The Real Thing."

He returned to A&M in 1983. "Never Gonna Let You Go," a Barry Mann and Cynthia Weil ballad sung by Joe Pizzulo and Leeza Miller, matched "The Look of Love" at No. 4 on the Hot 100 and spent four weeks at No. 1 on the adult contemporary chart; Confetti (1984) added "Olympia," used as a theme for that year's Olympic Games, and "Alibis." In the same decade he produced Lani Hall's vocal on the title song of the James Bond film Never Say Never Again, produced Sarah Vaughan's final album, Brazilian Romance (1987), which includes "So Many Stars," a song he co-wrote, and produced Yasuko Agawa's Ouro do Manaus (1988).

Brasileiro (Elektra, 1992), made with Carlinhos Brown, Hermeto Pascoal, songs by Ivan Lins and a studio band that included Nathan East and the drummer Jeff Porcaro, won the Grammy Award for Best World Music Album at the 1993 ceremony. Timeless (Concord, 2006), produced by will.i.am, set Mendes beside the Black Eyed Peas, Erykah Badu, Jill Scott, John Legend, Justin Timberlake, Q-Tip and Stevie Wonder; its remake of "Mas que nada" with the Black Eyed Peas reached No. 6 on the UK singles chart, and the album won the Latin Grammy for Best Brazilian Contemporary Pop Album, as Bom Tempo did again in 2010. With Carlinhos Brown and the lyricist Siedah Garrett he co-wrote "Real in Rio" for the animated film Rio (2011), a nominee for the Academy Award for Best Original Song, and he co-produced the soundtracks for Rio and its 2014 sequel. Magic (Okeh, 2014) and In the Key of Joy (Concord, 2020) were his last albums.

Mendes gave his final concerts in November 2023, in Paris, London and Barcelona. He passed away on September 5, 2024, at a hospital in Los Angeles, at the age of 83, from complications of long COVID. His wife and musical partner of more than five decades, Gracinha Leporace, was with him.

Mendes is best understood as a pianist and bandleader who began in jazz and became one of the most commercially successful Brazilian pop artists of his generation, and the two halves of his career are best kept distinct. The early records, from Dance Moderno through the Atlantic albums and his dates with Cannonball Adderley and Herbie Mann, are piano-led bossa nova by a jazz-trained player, mixing Brazilian originals with American standards, and he made a jazz album again with Sergio Mendes' Favorite Things (Atlantic, 1968) while the A&M hits were running. From 1966 the formula was different: English-language pop and rock songs (the Beatles, Burt Bacharach, Joni Mitchell, Buffalo Springfield) set over Brazilian percussion, with a lead female voice that Herb Alpert double-tracked in the manner of Les Paul and Mary Ford. By the 1980s the records were adult contemporary pop, and in the 2000s they were collaborations with hip-hop and neo-soul artists. The subgenre tags above are the nearest canonical ones, and they describe a crossover career, not a straight-ahead one.

Antonio Carlos Jobim was the formative influence, and the visiting American players he accompanied in Rio de Janeiro and New York in the early 1960s are where his jazz credentials were made. His clearest mark on the jazz repertoire is "So Many Stars," which he wrote with Alan and Marilyn Bergman for Look Around; singers including Sarah Vaughan, Tony Bennett and Stacey Kent have recorded it. The late-1990s lounge revival brought fresh attention to the Brasil '66 albums.