The vessel was attacked on Friday morning near the Iranian port of Chabahar, the Xinhua news agency said.
Chinese authorities immediately asked Iran to take the necessary steps to rescue the ship and crew, Xinhua said.
It is unclear what nationality the hijackers were. Most hijackings are carried out by Somali pirates.
In recent years Somali pirates have extended the reach of their operations right across the Indian Ocean
The vessel, the Xianghuamen, belongs to the Nanjing Ocean Shipping Co Ltd based in Nanjing, eastern China. One report said the ship was sailing with a crew of 28.
Chinese vessels have been attacked several times by pirates as they traverse international waters around the Arabian Sea.
China also plays a role in the international naval operation to fight piracy off the coast of Somalia.