The New York-based ratings agency cited the country’s prudent policy and improved monetary transmission.
Also, Fitch ratings agency said that Russia's long-term foreign- and local-currency issuer default ratings will remain at BBB- with positive outlook.
"Fitch Ratings has affirmed Russia's Long-Term Foreign- and Local-Currency Issuer Default Ratings (IDRs) at 'BBB-' with positive outlook," the release said on Friday.
Fitch explained that the positive outlook reflects "continued progress in strengthening the economic policy framework underpinned by a more flexible exchange rate, a strong commitment to inflation- targeting and a prudent fiscal strategy."
"The sovereign rating upgrade to the investment grade is a belated reaction to Russia’s successful economic policy," Maxim Oreshkin said.
Oreshkin suggested that Russia’s responsible macroeconomic policy had led to the US credit agency’s change of heart.
He said a flexible exchange rate system, "inflation targeting" and new budget rules had reduced the country’s reliance on oil prices, driving its ratings upward.
Oreshkin also noted that S&P's revision of Russia’s sovereign rating would open up the country to foreign capital. "An upgraded investment-grade rating will attract capital and keep the rate of return in the long-term Federal Loan Bonds market below 7 percent. This opens a path toward a rise in investment crediting and creates more opportunities for infrastructure loans," he said.