Toni is a free agent after being released by Bayern Munich.
Preziosi said: "He will be unveiled next week at the Genoa Foundation.
"Luca is the biggest investment in our history. He will give us satisfaction.
"Genoa's situation is one of calm. Our squad is already 90 per cent complete and the fact we don't have to make any further sacrifices is positive.
"We must only defend what we already have like Criscito and Papastathopoulos whose futures have been confirmed."