Iranian Energy Minister Hamid Chitchian and German Minister of Economic Affairs Sigmar Gabriel witnessed the ceremony.
Siemens was the first major German company to agree a deal with Iran this year, signing a memorandum of understanding to work on Iran's rail infrastructure worth up to 1.5 billion euros ($1.6 billion) in early January.
Mapna will acquire the technology to manufacture Siemens F-class gas turbines in Iran and the two parties will cooperate to deliver more than 20 gas turbines and associated generators over the next decade.
'With these important agreements we reinstall the long-term energy partnership between Mapna and Siemens,' said Siemens Chief Executive Joe Kaeser, who was present at the signing ceremony, according to Reuters.
Kaeser visited Iran last week and said Siemens wanted to pick up where it left off in Iran, where it had been present since 1868 but stopped doing new business in 2010.
As a first project under the energy deal, Siemens will deliver two F-class gas turbines and generators for a power plant in the southern port of Bandar Abbas, with the first unit due to be shipped shortly.
Siemens also signed a memorandum of understanding to jointly develop a roadmap with Mapna to expand and improve Iran's overall power and electricity system.