Born Henry Saint Clair Fredericks in New York City (but raised in Springfield, MA) to a gospel-singing South Carolina schoolteacher and a piano-playing West Indian jazz arranger, his passion for the blues began while he was attending the University of Massachusetts in the early '60s. He fell in love with the music of such performers as T-Bone Walker, in which he saw an important African musical tradition that represented for every aspect of life. By keeping the music alive, he would be preserving the African heritage he cherished. In addition to his regular studies, Mahal began to delve into blues history, which led him to explore other forms of Black folk music as well, including West African music, Caribbean, and zydeco, in addition to R&B, rock and jazz. He already knew how to play the bass, but soon also learned to play the instruments used by old-time musicians, including piano, acoustic guitar, banjo, mandolin, dulcimer, harmonica and assorted flutes. Armed with new knowledge, he began playing the Boston folk circuit.

Following graduation with a BA in Agriculture in 1964, Mahal went to Los Angeles and teamed up with guitarist Ry Cooder to form the Rising Sons, but the band released just one single before breaking up, although more than 20 tracks recorded by the group surfaced on CD in the 1990s. Mahal made his own recording debut for Columbia in 1968 with a self-titled album. He recorded several more albums for the label through the early '70s and at the same time established himself as a popular, charismatic, yet laidback performer, known for his adventurousness, gentle wit and intelligence. As the years have passed, Mahal has become known as a musical chameleon, changing and mixing up genres to suit his current interests. He has even recorded children's albums that are anything but childish in their content. Many albums, such as Like Never Before (1991) contain an eclectic assortment of styles covering both old songs and his new compositions.