Ferrer, who lost just one set in the tournament, needed just more than an hour to finish off a 6-3, 6-4 victory over Petzschner. He won more than three-quarters of the points on serve even though he dropped serve once. Ferrer lost only three points in five service games of the second set.
Ferrer had two breaks in the first set and one in the second.
He adds the UNICEF title, which was decided on a grass court, to wins this year in New Zealand (hard court), Argentina and Mexico (both clay courts). Ferrer is 15-15 in ATP championship matches.
Saturday marked the third tournament title match for Petzschner, who was a winner in October 2008 but has been the runner-up the other two times.
Both players head next to the Wimbledon Championships. Ferrer, seeded seventh in the major tournament, drew Dustin Brown in the first rounds while the unseeded Petzschner will face Blaz Kavcic in his opener.
Wimbledon, the year's third Grand Slam event, begins Monday.