The Serb defeated Tomas Berdych 6-2 6-2 at the ATP World Tour Finals to book his place in the last four and end the year as the world's best player for the third time in his career.
Djokovic becomes the third player to achieve that feat - joining Pete Sampras (six), Jimmy Connors (five), Roger Federer (five), Ivan Lendl (four), John McEnroe (four) and Rafael Nadal (three).
The 27-year-old also become a father for the first time and won Wimbledon, so the 27-year-old reflected on his season with a great deal of pride.
"I'm delighted to be standing here knowing all the legends who have done the same," he said. "Looking at the history and how many players have made a mark in this sport is something I appreciate very much.
"Professionally, [this is] probably the best year of all. To be able to stand here next to this trophy [for ending the year as number one] and basically have the crown for all the achievements is amazing and very fulfilling.
"I'm full of joy."
Djokovic will meet Japan's Kei Nishikori in the semi-finals in London and says Saturday's last-four clash means his celebrations will be limited.
"The tournament is not over so I have maybe a few hours of celebration but then it's the semi-finals and preparing for that," he added.