ENI has made large natural gas discoveries in the deep waters off Mozambique's northern coast over the past three years.
The country is only just getting to its feet after a devastating 16-year civil war that ended in 1992.
The delegation also included Italy's main business lobby, Confindustria.
Renzi became the first Italian head of government to visit Mozambique on Saturday at the start of an African tour.
During a champagne lunch with President Armando Guebuza, Renzi said the
visit was the result of an invitation made in Brussels earlier this year.
"I am sure he did not actually think I would come but I am here," Renzi said
Guebuza called the relationship between the two countries "excellent".
"We have watched with great satisfaction the gradual flourishing of economic cooperation and business ties," he said, pointing to Italy oil major ENI's presence in the energy sector.
Mozambique boasts some of the world's largest untapped natural gas reserves, with up to 170 trillion cubic feet discovered so far.
Uncertainty surrounds the start-up date for the construction of the first gas-to-liquid facilities to begin exploitation by 2018.
ENI and Texas-based Anadarko have yet to make a final investment decision on liquefied natural gas (LNG) facilities as they await new petroleum laws to govern the sector.
Whereas the government has asked the two companies to collaborate on the first LNG onshore, ENI is believed to be pushing to construct a separate, floating LNG facility out at sea.
The Mozambican government estimates an initial $50 billion dollar investment is needed to get natural gas into production.
"We are sure that this investment will pay off," Renzi said, adding that "$50 billion will go not only into the gas project, but also more broadly, into the growth of the country."
Italy and Mozambique share close ties, despite the lack of previous official visits from an Italian leader.
Italian religious leaders and diplomats mediated the process that culminated in a peace treaty signed in Rome.
From Mozambique, Renzi will travel to the Democratic Republic of Congo and oil-rich Angola, where ENI also has interests.