World number one Novak Djokovic completed a terrific week by setting two more records in winning the Paris Masters on Sunday.
Russia's Medvedev, 25, broke Djokovic's serve twice as he took the first set.
But the Serbian, who will end the year as number one for a record seventh time, eased through the final two sets.
Loose games from Medvedev, who denied the Serbian a calendar Grand Slam in September at the US Open, handed Djokovic two crucial breaks in the deciding set.
Both Djokovic and Medvedev will play the season-ending ATP Tour Finals in Turin, starting on 14 November, where Medvedev will attempt to defend his title.