Djokovic jumped into the air off all its feet at once to celebrate his third win in the year-end tournament with a 6-3, 6-4 victory in one hour and 36 minutes.
The Serb also extended his winning streak to 22 matches. He has been unbeaten since losing Nadal in the US Open final Sep 9.
Nadal, who still leads Djokovic with 22 wins against 17 defeats, is still waiting for his first win in the event. He entered the final for the first time in 2010 but was defeated by Roger Federer.