Castelen has joined the A-League outfit from Dutch top flight club RKC Waalwijk on a two-year contract and will be eligible to play in next month's ACL quarter-final against China's defending champions Guangzhou Evergrande.
"I am excited by the new opportunity," said the 31-year-old, who played 10 times for his country.
"The Wanderers is a great club, they have a great coach and a big fan base. I like to play in front of big crowds and I looked on the internet and saw how passionate the fans are.
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"I am very much looking forward to being a part of the growth of the Wanderers."
The Wanderers have attracted a particularly passionate following in their first two seasons after being launched by the A-League as an expansion team in April 2012.
They have lost marquee player Shinji Ono, who helped them to the A-League final in both of their first two seasons, after the Japanese playmaker decided to finish his career at home.
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