Guerin, a 15-year NHL veteran, signed a two-year deal with the Islanders last week. He becomes the 11th captain in team history.
"This is an absolute honour and a responsibility I will not take lightly," Guerin said in a statement. "Coming to a team with such a rich tradition and history is special in itself, but wearing the 'C' is something much greater.
"I'll do everything I can to make the Islanders organization and our fans proud."
General manager Garth Snow said the decision was an easy one for him and head coach Ted Nolan to reach.
"Bill is the epitome of what being a captain stands for, so this was an easy choice," Snow said. "Ted and I discussed it at length over the weekend and felt it was a fairly easy decision."
Guerin, 36, had 36 goals with 20 assists in 77 games last season with both the St. Louis Blues and San Jose Sharks. Guerin has 364 goals and 355 assists in 1,026 career NHL games.