Seppi dropped the first set 3-6 before resorting to a tiebreaker to take the second frame 7-6 (7-3), then dominated the third set 6-3 to register his second title of 2012.
The Italian improved to 3-3 in career finals following Sunday's triumph as well as May's victory in Belgrade.
Seppi also has reached finals in Eastbourne and Metz this year.
Bellucci, meanwhile, fell in his quest for a second 2012 crown following his July victory in Gstaad.
Wisconsin business offering 'therapeutic cuddling' forced to close
Selena Gomez drops F-bomb, walks off stage during Jingle Ball performance