The 27-year-old Dutch youth international keeper departs with the MTN8 success to his name, won under former head coach Benni McCarthy in 2018.
He follows Greek defender Giannis Potouridis out of the club, while Jan Olde Riekerink was replaced by Eric Tinkler as head coach last week - as plans for next season begins early in the Mother City.
"Thanks for making me feel at home, the last three years have been an absolute pleasure. Life-changing moments on and off the pitch," he wrote on social media.
"[I've] met so many special people from all kind of cultures and backgrounds. More than ready for the next step. Siyabonga. Baie dankie. With love."
With league outings against Black Leopards and Mamelodi Sundowns remaining, young keepers Marc Anderson or Bombay Reid are likely to step into the role Leeuwenburgh has vacated.