The at-large delegates each will cast one vote at the Republican National Convention this summer. Three "superdelegates," who are not bound by Sunday's results, also have pledged to back McCain, the front-runner for the Republican presidential nomination.
The delegates from Puerto Rico helped McCain move closer to clinching the GOP nomination, giving him a total of 996 delegates. His rival, former Arkansas Gov. Mike Huckabee trails McCain with 254 delegates.
It will take 1,191 delegates to secure the Republican nomination.
On Saturday, McCain picked up all nine delegates awarded by the GOP in American Samoa, as well as the nine GOP delegates from the U.S. Commonwealth of the Northern Mariana Islands.
In a letter to Luis Fortuno, Puerto Rico's nonvoting congressional delegate and a superdelegate, McCain pledged to support a process that would enable Puerto Ricans to decide if they want to remain a commonwealth, become a state or an independent nation.
"The people of Puerto Rico deserve a process of self-determination and a congressionally defined referendum that gives them a fair and unambiguous choice among status options," McCain wrote. "That is one of the many important things that we will accomplish together."