Ahmadinejad, making a two-day stop in Hanoi on the way home from the Bali Democracy Forum, discussed economic links and other potential areas of cooperation with President Truong Tan Sang.
Speaking to reporters afterwards, Ahmadinejad hailed the "very friendly" relations between the two countries and said both sides aimed to strengthen their bilateral ties.
"We are determined to extend cooperation in different fields, including (the) economy, agriculture, industry, science and technology, culture, tourism and sport," he said, speaking through an interpreter.
It is the highest-level Iranian visit since 1995 to the communist nation, which is generally seen as supportive of Tehran's right to the peaceful use of nuclear energy.
Sang said cooperation between the two countries would be "accelerated" in the future. Ahmadinejad was also due to meet Prime Minister Nguyen Tan Dung for talks on trade and investment.
The two countries -- which established diplomatic ties in 1973 -- have previously signed a range of agreements to cooperate on oil and gas and infrastructure projects.
Iran is struggling under tough Western sanctions over its controversial nuclear activities. A shortage of foreign currency caused a plunge in the value of the Iranian rial last month.
Western powers suspect Tehran is using the programme to develop atomic weapons capability. Iran denies that and says its nuclear activities are purely peaceful.
A Hanoi-based diplomat said Ahmadinejad's visit was an attempt to seek diplomatic and economic support from a friendly nation but "lacked substance" as Vietnam is not in a position to help much given its own economic woes.