The Bank of Spain raised its forecast from an earlier estimate of 2.8 percent published in late March, its governor Luis Linde told parliament.
Prime Minister Mariano Rajoy is vaunting Spain's economic recovery as he prepares to fight a year-end general election, after passing austerity reforms and weathering numerous corruption scandals.
His government's official growth forecast currently stands at 2.9 percent for this year and it expects the expansion to continue at a comparable rate in 2016.
Spain officially exited recession in late 2013 and the economy grew by 1.4 percent last year as consumer spending and investment improved.
That was its first full year of growth since a property bubble burst in 2008, throwing millions of people out of work.
"The latest information indicates that activity is maintaining a strong rate of expansion," Linde said on Wednesday.
"The forecasts for the rest of this year and the next point to the maintaining of a high level of dynamism, markedly greater than that of most of our eurozone partners."
Linde forecast 2.7 percent growth in 2016. He was informing parliament of the new forecasts in the bank's annual report which is published on Thursday.
Despite the strengthening in Spain's growth figures, the country's official unemployment rate remains extremely high.
It was 23.7 percent at the last count in the first quarter of this year.
The government says the number of registered unemployed has been declining over recent months.