Talking to reporters in Tehran, Chavez said that he hoped Iran would invest in Venezuela's Orinoco region.
"We invite Iranian companies to the Gulf of Venezuela and the delta for gas production," he said on a visit to Iran as part of a four-nation mission that included Qatar, Russia and Belarus.
Iranian investment in Venezuela last year was worth $1 billion, most of it in oil and gas and engineering sectors.
Venezuela and Iran are both members of the Opec and fierce critics of the US and the pair pledged to stand by each other in their struggles with the United States.
Chavez met Ahmedinejad on Saturday and said his country would "stand by Iran at any time and under any condition", Iran's state-run television reported.
Ahmedinejad said, "I feel I have met a brother and trench-mate after meeting Chavez.
"We think Iran and Venezuela should share all experiences of each other, stay by each other and they have to be supporters of each other."
During his visit, Chavez was to inaugurate the new Venezuelan embassy in Tehran and Iranian state television reported that he was also to meet Ayatollah Ali Khamenei, Iran's supreme leader.
Ahmedinejad said: "We do not have any limitation in co-operation. Iran and Venezuela are next to each other and supporters of each other.
"Chavez is a source of a progressive and revolutionary current in South America and his stance in restricting imperialism is tangible."