Kohn, a 20-year-old from Edmonton, was selected by the Islanders in the second round of the 2005 NHL draft. He spent three seasons in the Western Hockey League with the Calgary Hitmen before joining the Brandon Wheat Kings in 2006.
At the end of the 2005-06 season, the six-foot-one, 190-pounder also played two regular-season games with the Islanders' American Hockey League affiliate in Bridgeport.
"Dustin has all the tools of an NHL-calibre defenceman," Islanders general manager Garth Snow said in a statement. "Now that Bruno Gervais and Chris Campoli have developed within our system to become effective players in the NHL, Dustin is one of our prospects on the blue-line who could eventually be next."
The Islanders begin training camp this September in Moncton, N.B.