According to Mokonyane, she became active in the anti-apartheid struggle in the late 1970s at the age of fifteen, first as a member of the Young Christian Students and then as a founding member of the Congress of South African Students in 1979. In the 1980s, she was a member of the United Democratic Front; an organiser for the Federation of Transvaal Women (FEDTRAW); a shop steward in the Commercial, Catering and Allied Workers' Union of South Africa; and a leader in the civic movement of her hometown through the Kagiso Residents' Organisation.