The 31-year-old striker, who has scored over 100 goals for Banyana, announced the decision today at Safa House.
Safa president Danny Jordaan announced that "her new role will be to guide other players".
"This is a special moment. This is one player who knew how to get the ball into the net," Jordaan says.
"We're going to create a coaching path for Portia. We certainly hope she will pursue a coaching career."
Modise made her national team debut in 2000 and made 117 appearances for the team, scoring her 100th goal in October last year against Algeria at the CAF African Women's Championship.