India has signed a $40bn (£21bn) deal to import millions of tonnes of liquefied natural gas from Iran.
Iran is among the world's top producers of gas
Firms led by the Oil & Natural Gas Corporation (ONGC) will also assist in the development of Iranian oil fields.
Ministers, eager to gain access to energy supplies to meet the demands of a booming economy, secured a similar deal to one between Iran and China.
The announcement comes as ONGC said it was in talks to buy former assets of troubled Russian oil firm Yukos.
The agreements with Iran were sealed after talks in New Delhi between Middle East producers and Asia's biggest energy consumers - China, India, Japan and South Korea.
Soaring oil demand
Iran - Opec's second-biggest oil producer and one of the world's top gas producers - has been pursuing a series of deals, rewarding LNG buyers with participation in development of its oil fields.
Under the agreement, it will supply India with 7.5 million tonnes of LPG annually over a 25 year period from 2009.
ONGC and the National Iranian Oil Company (NIOC) reached a preliminary deal for Indian firms to take part in the development of the Yadavaran and Jufeyr oilfields, both countries said in a statement.
India's oil production has stagnated over recent years, and it is having to look abroad to secure future supplies. India imports about 70% of its total oil consumption.
Consumption has jumped to 2.4 million barrels per day, compared with 474,000 bpd in 1973.