Sheena Duncan was born in Johannesburg in 1932 and was the eldest of the five children in her family. She was educated at the Roedean School in Johannesburg, and in 1953 she went abroad to study domestic science at the Edinburgh College of Domestic Science. After she qualified as a domestic science teacher, she moved to Zimbabwe (then Rhodesia) and she lived there for eight years. On her return to South Africa, she worked as a Home Economics Officer in the Social Welfare Department of the Johannesburg City Council.
Her mother, Jean Sinclair, was one of the founders of Black Sash movement, in 1955, and its National President for fourteen years. Sheena joined the movement in 1963 to fight the political causes of suffering, especially those brought about by the pass laws. Always working in a voluntary capacity, she held various offices in the Black Sash movement, including regional chairman, editor of Sash magazine, and National President.
The Black Sash was known for the demonstrations and night vigils they held outside Parliament in protest of government legislation.
She wrote many articles and published booklets and pamphlets that were meant to help enlighten people about what was going on in South Africa with regards to Pass Laws and forced removals.
In the 1970s, Sheena joined the Anglican Church’s Challenge Group that was aimed at ending racism within the church. She was a member of the Church's Provincial Synod and represented the Anglican Church on the South African Council of Churches (SACC) Justice and Reconciliation Division. She was titled with the position of Honorary Life President of the SACC, and chair and patron of Gun Free South Africa. She also lectured frequently in South Africa and in other countries and attended many international conferences.
Duncan received the Order of the Baobab in 2006, “for her excellent contribution to the struggle for a non-sexist, just and democratic South Africa”.
Sheena Duncan passed away peacefully, at her home in Johannesburg in the early hours of the morning on 04 May 2010. Duncan leaves two daughters and two grandchildren.