The game is set to be played at the FNB Stadium on May 16.
Sundowns confirmed the news via their Twitter page on Friday.
— Mamelodi Sundowns FC (@Masandawana) 4 May 2018
This will be the second time the teams meet in South Africa.
In 2007, Barcelona came from a goal down to beat Sundowns 2-1 at the Loftus Versfeld Stadium.