The court ruled that the decision was inconsistent with the Constitution.
The decision to grant her diplomatic immunity was taken by former Minister of International Relations and Cooperation Maite Nkoana-Mashabane after Mugabe allegedly assaulted Gabriella Engels in a luxury hotel in Sandton in August last year.
Rights group AfriForum and the Democratic Alliance (DA) challenged the decision by the department.
Today’s decision comes as Zimbabweans vote in their first election since Grace’s husband Robert was ousted last year.
Engels suffered cuts and bruises to her head following the alleged assault by Mugabe.
Previously, AfriForum said various other institutions had brought similar applications and would join the proceedings as friends of the court.
These are the Commission for Gender Equality, Freedom Under Law and the Women’s Legal Centre, who were all present in court.
The DA’s federal council chairperson James Selfe also attended the judgment.
The DA said condoning such behaviour could not be in the interest of South Africa or justice.
Engels previously told News24 that should they be successful in challenging the decision to grant Mugabe diplomatic immunity, they would like to see criminal proceedings instituted against Mugabe.- News 24