The Czech, who beat Jo-Wilfried Tsonga in the final, has reached the year-ending showpiece for the world's top eight men for the third year in succession.
Berdych reached the semi-finals at the O2 Arena last year, losing to eventual runner-up Tsonga, and had enjoyed another consistent year, reaching the last eight at the Australian Open and the semi-finals of the US Open.
Two more spots are up for grabs with two weeks of the regular season remaining, although already-qualified Rafa Nadal is a major doubt having not played a match since Wimbledon because of recurring knee problems.
Argentina's Juan Martin del Potro and France's Tsonga are in seventh and eighth positions in the race to London with Serbia's Janko Tipsarevic in ninth place.
Results from this week's tournaments in Valencia and Basel and next week's Paris Masters will determine the line-up for London's fourth staging of the Tour Finals.