President Putin announced that Russia would build a series of nuclear plants in India over the next two decades.
He said work on the first two reactors was now in preparation.
About $7bn (Â£4.7bn) worth of deals have been signed during Mr Modi's Russia trip, many of them defence related.
However, there has been no progress on an expected purchase by India of Russian S-400 missiles, Moscow's most sophisticated aircraft defence system.
"I see in Russia a prominent partner in India's economic transformation," Mr Modi said after he and Mr Putin agreed to reduce visa requirements between the two countries.
Mr Modi is eager for Russia to participate in various infrastructure projects as his government strives to revamp India's railway network and build nuclear energy plants to meet growing electricity needs.
They agreed on the location of a new Russian nuclear energy plant in the southern Indian state of Andhra Pradesh.
Russia is already constructing a nuclear plant in the nearby state of Tamil Nadu. Mr Modi said Russia had agreed to build a total of 12 over an unspecified timeframe.
Deals signed between the two countries included:
President Putin told a joint briefing that Russia supported India's "strengthening role in resolving global and regional problems".
He said India was "among the most honourable candidates" for permanent membership of the United Nations Security Council.
Russia and India were close allies during the Cold War, but recently the relationship has become more complex.
Talks have been held annually since 2000 and hosted alternately by Moscow and Delhi.
Bilateral trade stands at $10bn (Â£6.74bn) - and Russia is India's second largest defence supplier.
But earlier this year, India was reported to be displeased with Russia for selling attack helicopters to Pakistan.
Russia was unhappy with India for choosing French Rafale fighters and American Apache attack helicopters over Moscow's defence products.
Russian President Vladimir Putin and Indian Prime Minister Narendra Modi have proclaimed the partnership between their two countries as they signed defence, energy and other deals.