The number for gross domestic product was initially reported at 2.3 per cent on July 30.
The sharp upward revision was mainly due to higher investment, state and local government spending, and consumer spending than was reported in the first estimate, the department said.
The GDP report widely topped analysts' consensus estimate of a pick-up in the world's largest economy to a 3.1 percent pace following a tepid first three months of 2015.
In the first quarter, the economy grew only 0.6 percent under pressure from severe winter weather and West Coast port strikes.