On March 4, 2009, the Islanders traded Guerin to the Pittsburgh Penguins in exchange for a third-round pick in the 2009 NHL Entry Draft. On June 12, 2009, Guerin won the Stanley Cup after the Penguins defeated the Detroit Red Wings 2–1 in Game 7 at Joe Louis Arena. On June 29, 2009, Guerin signed a one-year contract extension with the Penguins with a greatly reduced salary to play through the 2009–10 NHL season. He was not offered a contract for the 2010–11 NHL season.