The 20-time Grand Slam champion, who will be confirmed as world number one on Monday, beat the world number five 6-2-6-2 on Sunday for his 97th title.
Federer, who had previously won in the Dutch city in 2005 and 2012, broke in the fifth game as Dimitrov made 13 unforced errors in the first set.
Dimitrov appeared to be carrying an injury throughout the second set, although he was able to break his opponent's serve, but the Swiss maestro soon regained control to win the match in 55 minutes.
Federer first became world number one in February 2004, but has not topped the rankings since October 2012 and slipped to a low of 17th in January 2017 following six months out with injury.
Since then, the 36-year-old has won eight titles, including Wimbledon last year and two Australian Opens.