The cargo ship, which belongs to Iran's Valfajr Shipping Company and contains 2,500 tons of humanitarian aid, left Iran for the Yemeni port of Hodeida on Monday evening.
It has been loaded with 700 tons of flour, 1200 tons of rice, 400 tons of canned food, 50 tons of medication and health products, and 50 tons of mineral water.
There are 60 people on board the ship, including 15 medical staff, 13 journalists and 7 peace activists from the US and Europe.
The vessel set sail from Iran's southern port city of Bandar Abbas, and is destined for Yemen's western port of Hodeida through the Sea of Oman, the Indian Ocean, the Gulf of Aden, the Bab-el-Mandeb strait and the Red Sea.
The ship's journey comes after Yemen agreed to a five-day truce proposed by Saudi Arabia, beginning Tuesday.
The ceasefire, which is to allow humanitarian aid in, is to come into force at 11pm (2000 GMT) on Tuesday.
On March 26, Saudi Arabia and some of its Arab allies began to launch deadly air strikes against the Houthi Ansarullah movement in an attempt to restore power to the fugitive former President Abd Rabbuh Mansour Hadi, a close ally of Riyadh.
Some seven weeks of deadly aerial attacks on Yemen have killed over 3,500 people and left some 6,200 others injured.