The visit to Tehran is the sixth by Chavez, a vocal supporter of Iran's right to develop a nuclear programme and critic of the US.
"Arriving in Tehran for us is like arriving at one's own home," Chavez said in remarks carried on state-run television.
Chavez has said a joint Venezuelan-Iranian development bank would be inaugurated during his visit. He said the two nations would each put $100m into the bank.
"The big banks of the world have sunk, but here a new bank is being born," he said.
Previously, Chavez founded the Bank of the South along with allied governments in Latin America in an effort to create a homegrown alternative to the World Bank and International Monetary Fund.
"I hope President Obama is the last president of the Yankee empire, and the first president of a truly democratic republic"
When asked about Obama's recent overtures to Iran for improved relations, he said that he was not optimistic.
"I don't have much hope, because behind him is an empire. He's the president of an empire. ... Now, I think it's fair to give him some time ... seeing is believing,'' Chavez said.
"I hope President Obama is the last president of the Yankee empire, and the first president of a truly democratic republic, the United States."
Washington broke off diplomatic relations with Iran after the revolution in 1979 and the takeover of the US embassy in Tehran.
Ties further deteriorated under George Bush, the former president, but Obama has struck a different tone since taking office, saying he would like to have engagement with Tehran.
Venezuela's relations with Washington are also strained, with Chavez expelling the US ambassador and recalling his own envoy from the US last September.