Born in Kingston, Jamaica, Campbell's singing career began in church, where his father was a preacher, and Al would sing to raise funds. He went to school with Lloyd James (aka Prince Jammy) and formed a vocal group with friends as a teenager, called The Thrillers, who recorded in the late 1960s for Studio One. After briefly joining up with Freddie McGregor and Ernest Wilson, he went on to work with Prince Lincoln Thompson's Royal Rasses, and the Mighty Cloud band.Campbell then embarked on a solo career (also contributing vocals to two Heptones albums), and was a popular roots reggae singer during the 1970s, recording for producers such as Phil Pratt, Bunny Lee, and Joe Gibbs, and recorded at Lee Perry's Black Ark studio. His "Gee Baby" was a big hit in 1975 in both Jamaica and the United Kingdom. He adapted successfully to the early dancehall and lovers rock styles in the late 1970s and 1980s, working with producers such as Linval Thompson. Campbell's recording of "Late Night Blues" (1980) became a staple of blues parties. Campbell performed with the Stur-Gav sound system in the early 1980s. More recently he has recorded for King Jammy, Philip "Fatis" Burrell, and Mafia & Fluxy.

In 1997, he joined Cornell Campbell and Jimmy Riley in a new version of The Uniques, the group releasing a self-titled album in 1999.