The Log Cabin Republicans endorsed McCain, R-Ariz., Tuesday at the Republican National Convention in St. Paul, Minn., CNN reported.
"He's a very inclusive Republican, a different type of Republican," said the group's president Patrick Sammon. "At the same time, we have honest disagreements on some issues."
While McCain opposes same-sex marriage, he also opposed a federal constitutional amendment that would have defined marriage as being between a man and a woman.
While McCain's running mate, Gov. Sarah Palin of Alaska, has expressed support for the federal amendment, she vetoed a bill that would have banned her state from giving benefits to same-sex partners of employees.
"She's a great choice," said Log Cabin member David Valkema of Illinois. "We're learning more every day but what we know, we like."