Newsom said on Tuesday that he has already sent the team's flag to Atlanta Mayor Kasim Reed to honor their bet.
The two mayors had agreed to hoist the winning team's flag over the losing team's City Hall. The losing mayor must also welcome the winner to his city for a personal, behind-the-scenes tour of its best attractions.
Newsom joked that he couldn't imagine the indignity of having to raise the Braves' flag at San Francisco City Hall and feels for Reed.
Newsom is trying to come up with a similar bet with Philadelphia Mayor Michael Nutter. The Giants now face the Phillies in the National League Championship Series.