The figures were revised up from a growth pace of 1.3% previously reported.
Compared with the first quarter, the gross domestic product increased 0.5% in the April-June period, up from a quarterly rate of 0.3% initially estimated.
First-half growth was also slightly faster than previously thought. The new numbers show an annual increase of 1.8% in the first six months, from a growth rate of 1.7% announced earlier.
The industry contributed 1.1% to the GDP growth in the first half, while real estate deals and agriculture made positive contributions of 0.3% and 0.2%, respectively, INS data showed.
On the other hand, constructions had a negative impact of 0.2% on the Romanian economy in the first six months of 2013.
Final consumption was flat on the year in the first half, but gross capital formation declined 1%.
Net exports, however, contributed 5.3% to the first half GDP, the data showed.
Romania forecasts an economic growth of 2% in 2013, largely supported by agriculture and exports.