The 26-year-old joined the Cottagers in January for £12million, but he started just one game for the club as they were relegated.
Now Fulham are looking to move the Greece international, and Hertha were linked with a possible loan - but they have ruled out making a move.
Hertha Berlin manager Jos Luhukay told the club's website: "Should we manage to find a very good striker, we may make some further business, of course.
"There is no truth in rumours linking Hertha Berlin with Konstantinos Mitroglou, definetely no truth! We are looking to sign (a striker) but we have no pressure as we already have a good first XI."