The construction, named Saint Pierre Han, was built in 1771 by French architects, reports Xinhua news agency.
It is located in the Banks Street, one historic spot that used to be renowned as the financial hub of the late Ottoman Empire.
Speaking at the ceremony on Monday, Imamoglu said the building will be used as a cultural centre to host temporary and permanent exhibitions after restoration.
"We have a responsibility to protect our heritage, bring it back to life, and transfer it to future generations," Imamoglu added.
The historic building originally housed French interests in Constantinople including the French National Bank.
From 1856 to 1893, it was the home of the Ottoman Bank.
The building also hosted the Constantinople Bar Association, the Italian Chamber of Commerce, several architects, and a mustard factory.