Achmat set fire to his school in Salt River in support of the 1976 student protests and was imprisoned several times during his youth for political activities. He joined the African National Congress (ANC) in 1980 while serving time in prison. Between 1985 and 1990 he was a member of the Marxist Workers Tendency of the ANC, a Trotskyist breakaway group of the ANC and precursor to the Democratic Socialist Movement.