The statesmen hit the green at a marine base on the northeastern coast of the island of Oahu yesterday, according to journalists at the scene.
Obama and his family are spending more than two weeks in Hawaii and have rented a house near the base, located about 20 kilometres from Honolulu, where Obama was born.
The two men, joined by Key's teenage son and White House aide Marvin Nicholson, hit several balls and joked around in front of reporters.
Yesterday marked Obama's eighth round of golf during his vacation, which hit the 13-day mark. The president usually plays with friends or colleagues and has even teed off with White House chef Sam Kass.
In contrast to his predecessor George W Bush, who hosted foreign counterparts at his ranch in Crawford, Texas, Obama prefers to surround himself with family and friends during his time off -- usually spent in Hawaii at the end of the year and Martha's Vineyard in the summer.
Obama is due to leave Hawaii aboard Air Force One on Sunday to return to Washington, an eight-hour flight away.
