The 28-year old Dutchman was offered a contract extension by United but has decided to take up a very good deal with the K-League outfit after heading over for a few days last month to hold talks with the club and view their facilities.
van den Brink said he was looking forward to a new challenge although he knows it will be hard to leave the Gold Coast.
"I've had a fantastic time at Gold Coast United and will miss the club, the fans, my teammates and the area. But the deal put forward from Busan I'Park was a very, very good one and I would be mad to turn it down," he said.
"Footballers can sometimes have a short career so when you receive a good offer you have to give it your full consideration and make decisions that benefit your family and career.
"The Gold Coast United supporters have been just brilliant to me and I would like to thank them, Clive Palmer and Miron Bleiberg for all their encouragement throughout my time here. From now until the end of the season I will be doing everything I can to make sure this year ends in success for the club.
"Had it not been for this offer from Korea I would have been delighted to stay at Gold Coast United. It was a difficult decision but now that it's out in the open I just want to concentrate 100% on making sure we push for success and end this season on a high."