Pelech, 22, had three goals and seven assists in 44 games as a rookie for the Islanders last season. He had one goal and four assists in 13 games for Bridgeport of the American Hockey League. He was a restricted free agent.
"Adam has proven at a very young age that he's capable of playing an important defensive role on our team," Islanders general manager Garth Snow said. "He will be an important piece of our defensive core moving forward and I'm excited to watch him continue to develop at the NHL level."
The Islanders selected Pelech in the third round (No. 65) of the 2012 NHL Draft. He has 12 points (three goals, nine assists) in 53 NHL games.
Defenseman Calvin de Haan and the Islanders have a salary arbitration hearing scheduled for Aug. 2 in Toronto.
