Mars was born in Laurens, South Carolina, United States to sharecropping parents. When he was aged fourteen, and on the death of his mother, Mars and his younger siblings moved to New Paltz, New York, and having left high school, Mars began playing in various clubs in New New York
Over a long career, Mars has worked with Magic Sam, Earl Hooker, B.B. King, Jesse Fuller, Spencer Davis, Ian Gillan, Do-Re-Mi, Bananarama and Michael Roach. His family regularly moved house when Mars was a youngster, but at the age of nine, he was presented with his first harmonica. By the mid 1960s, Mars had moved to California and formed the Johnny Mars Band, who found work but no recognition beyond their North California base.
However, they toured with Magic Sam, and played on the same bill as Earl Hooker, B.B. King and Jesse Fuller.
After advice from Rick Estrin (Little Charlie & the Nightcats), Mars toured the United Kingdom in 1972, and subsequently recorded two albums there before fully relocating to Somerset in 1978. Mars worked with the record producer, Ray Fenwick, plus Spencer Davis and Ian Gillan.
His 1984 album, Life on Mars, received critical acclaim. In 1988, Mars was a guest musician on the Do-Re-Mi album, The Happiest Place in Town.
Mars later worked with Bananarama on "Preacher Manitoba" (1990) and their 1991 cover of "Long Train Running", appearing in the group"s music video for the former track.
Mars also taught for 15 years in primary schools in England, and worked with teenagers in music projects. Mars continued touring across the United Kingdom and Europe where he had a strong fan base. In 1992, Mars played at the San Francisco Blues Festival.
In 1999, Mars released Stateside, and On My Mind followed in 2003.
In 2003 and 2004, Mars played with the The Barrelhouse Blues Orchestra. More recently, Mars teamed up with the blues guitarist, Michael Roach, and appeared at the Bath Music Festival (2008, United Kingdom), Pocono Blues Festival (United States) and the Kastav Blues Festival (Croatia).
In January 2010, the pair toured the Middle East.
He signed a recording contract with Mercury Records whilst a member of a band named Burning Bush, and they recorded several sides with the label.
