Less than 24 hours after Serena joined older sister Venus as a three-time gold medallist with a victory in the women's Singles - completing the career golden slam in the process - the USA pair saw off Czech Republic duo Andrea Hlavackova and Lucie Hradecka 6-4 6-4.
Today's match was a repeat of last month's Wimbledon final, which the Williams sisters also won in straight sets on Centre Court.
The USA duo broke serve in the very first game under a closed roof this time and although they were forced to save more than one break-back point, they held on to take the opening set.
Hlavackova and Hradecka had chances to break early in the second set before dropping serve themselves in game five and the Williams sisters never looked back.
We come in as the favourites. But it's not a given. We fought hard. Our opponents played well. They're very talented.Venus Williams
The bronze medal was won by Russian pair Maria Kirilenko and Nadia Petrova, who came from a set down to beat Americans Liezel Huber and Lisa Raymond 4-6 6-4 6-1.
Venus said: 'For us it's so exciting winning the gold together. For me it was amazing to watch Serena from the stands and see her complete the golden slam. So it's been amazing for us.
'We've been winning this title since 2000, but it's easier said than done. We come in as the favourites. But it's not a given. We fought hard. Our opponents played well. They're very talented. We're glad to keep the medal for us. It was great.'