Waters became involved in Trotskyist politics at a young age, and joined the Socialist Workers Party (SWP) in the 1960s. She became the editor of their youth paper, Young Socialist, and the national secretary of the Young Socialist Alliance.
In the early 1980s, Waters, along with Jack Barnes and others in the SWP leadership, began to reject the label of "Trotskyism" and the theory of Permanent Revolution, in favour of building links with the Cuban Communist Party and Sandinista National Liberation Front.
Mary-Alice Waters has also written a number of books such as the 'Feminism and the Marxism Movement', 'Capitalism and the Transformation of Africa' and 'Une Revolution Socialiste Est-Elle Possible aux Etats-Unis?'.