That was the same as first quarter growth of 3.5 percent, but marked a slowdown from the second quarter of 2012, when the Andean nation's GDP expanded 5.5 percent year-on-year.
The South American nation, which is OPEC's smallest member, saw its economy grow 5 percent in 2012. But growth is expected to slow this year due to slumping prices for commodities and the idling of its largest refinery for several months for an overhaul.
Decent economic growth and heavy state spending helped President Rafael Correa win a landslide re-election in February.
He is predicting growth of 3.7 to 4.0 percent this year, and an improved 4.5 to 5.1 percent growth in 2014.
The leftist government has said it plans to issue sovereign debt - perhaps this year or in the first quarter of 2014 - marking a return to international debt markets five years after defaulting on $3.2 billion of sovereign bonds.