Becoming an unrestricted free agent in the 2006 off-season, Sillinger joined his twelfth and final NHL team, the New York Islanders, signing on July 2, 2006. He continued where he left off from his career season in 2005–06 with 59 points in his first season with the Islanders. Helping New York to the post-season, he set another NHL record by competing in the playoffs for his eighth NHL team. In 2007–08, Sillinger played in his 1,000th NHL game on November 1, 2007, versus the Tampa Bay Lightning. His family joined him on ice for a pre-game ceremony honouring the achievement. Sillinger went on to tally an assist in the milestone game as the Islanders won 4–0. His second season with the Islanders was, however, cut short due to a hip injury that required microfracture surgery in February 2008. He finished the campaign with 26 points in 52 games.