Dlamini-Zuma defeated incumbent chairperson Jean Ping of Gabon, who had headed the steering body of the 54-member organisation since 2008.
Her victory comes after a hard-fought battle between herself and Ping. The French news agency Agence France-Presse reported on Friday that SADC had accused sitting AU chief Jean Ping, who is Gabon's foreign minister, of abusing AU resources in his election race. The SADC was backing Dlamini-Zuma.
Ping had earlier denied a South African news report that he was withdrawing from the race.