The 18-year-old defenseman, taken with the No. 4 pick of the 2012 NHL Draft, has played for the Western Hockey League team the past two seasons.
"I'm really happy to have the job," Reinhart said, according to the Islanders' website. "I've got to take a bigger leadership role and be more vocal and help the younger guys coming into the league. I've got to lead by example and also communicate with them. I think I'm ready to take a big step up."