DA leader Helen Zille was appointed deputy chairwoman of the National Council of Provinces (NCOP) on Tuesday, her party said.
Zille, also the premier of the Western Cape, would serve in the rotating position for a year. The position would then be given to a delegate from another province.
"We congratulate Ms Zille on her election and believe that this would add value to the NCOP," said DA MP Elza van Lingen.
"Indeed, the NCOP must assert its relevance in the legislative process and improve its stature in the eyes of South Africans," Van Lingen said in a statement.
The NCOP is mandated to ensure that provincial interests are taken into account in the national sphere of government.
It is chaired by former North West premier, Thandi Modise.