The 34-year old centre-half, who has previously played for the likes of PSV Eindhoven, NEC Nijmegen, FC Twente, Ajax and Roda JC, joins the Heart after 16 years playing professionally in his homeland.
“I have played all of my career in the Netherlands and now it is an exciting time to play abroad,” Wielaert said.
“So when Melbourne Heart contacted me, I was enthusiastic immediately.
“The Club sounds great, the city and the country too, so I am looking forward to giving everything for this Club and the people around it.”
Wielaert joins Harry Kewell, Massimo Murdocca and Iain Ramsay as new Heart signings so far this offseason.