"The coaching staff has spent the last seven months watching matches in Australia, Europe, Asia and South America to find the striker that has the skills and the mentality to fit into our team and the A-League. I am very confident Gerald is that player," he said.
"Gerald is physically strong, but his real strength is with the ball at his feet and bringing his team-mates into the match. He has been in excellent form with Heerenveen this season, particularly in the second half of the season, so hopefully he will be able to maintain that level of performance with us.
"Gerald is a top professional and a winner. He has obtained experience in some of the best and toughest competitions in world football such as the UEFA Champions Leaguem," van 't Schip added.
"The lessons he can provide to the younger members of our team at training and during the match will prove very important in helping to shape the Club's culture for many years to come."
Sibon was an over-23 member of the Netherlands Olympic Football Team during the 2008 Beijing Games, scoring twice in four starts alongside Roy Makaay and Ryan Babel as the Oranje were knocked out at the Quarter Finals, while he has also collected a swag of honours at domestic level.
Sibon has secured five Dutch Cup winners medals, including the 2009 title, three Eredivisie championships and the 2007 German Pokal Cup with FC Nurnberg, where he was a team mate of fellow Heart players Michael Beauchamp and Dean Heffernan.