Cosco has signed a 35-year lease and will spend US$707 million to upgrade port facilities, build a new pier and almost triple the volume of cargo the port can handle, reported China Daily.
The move is part of an effort to create a network of ports, logistics centres and railways to distribute Chinese products across Europe - in essence a modern Silk Road - hastening the speed of East West trade and creating a valuable economic foothold on the continent.
The Piraeus port in Athens can currently load and unload 1.8 million containers a year.
With a strategic position near the Straits of Bosphorus, the port also provides a way into the Black Sea region, central Asia and Russia.
Cosco aims to make the container port a hub to rival Rotterdam, Europe's largest port.
Many see the latest Cosco investment as just the beginning of a far broader scheme to access European markets.
By the end of the year China is expected to make a joint bid with a Greek company to create a $252.2 million logistics hub at Attica, near the port, to distribute goods from China into the Balkans and the rest of the continent. The Chinese are also in talks to buy a share in the struggling state-owned railway in Greece.