Real gross domestic product expanded at an annualized rate of 3.9 percent over the three-month period, the Cabinet Office said Monday.
The result outpaces Kyodo news agency's average market forecast for an annualized 2.6 percent increase.
On a quarterly basis, the growth translates to 0.9 percent growth from the April-June period.
Japan, the world's No. 3 economy, benefited from higher spending by consumers and businesses.
Private consumption, which accounts for about 60 percent of GDP, rose 1.1 percent from the previous quarter, the data showed. Corporate capital investments climbed 0.8 percent.