Fars News Agency is reporting that the Iranian fleet arrived in the Gulf of Aden after traveling some 4,000 maritime miles, and carried out a naval exercise in preparation for a potential clash with the pirates.
Iran said last month it was negotiating with pirates who seized a ship it had chartered but that it was ready to use force to free the vessel.
The Hong-Kong-registered cargo ship Delight, with a 25-strong crew and 36,000 tons of wheat, was attacked in November in the Gulf of Aden as it headed for the Iranian port of Bandar Abbas.
The attack was the second since August 21, when Iran's Diyanat cargo ship was hijacked after passing the Horn of Africa.
Iranian officials have warned that Iran is mulling over a military option against Somali pirates.