"Continued good growing conditions have been a major factor in the growth this quarter, and is reflected in both the milk production in agriculture and in meat and dairy manufacturing," Statistics NZ's national accounts manager Rachael Milicich said.
Westpac's Stephens said encouragement could be taken from the fact that growth in the quarter was broad-based.
The result follows a similarly strong outcome in Australia, which earlier this month recorded a 1.3 per cent gain in quarterly GDP growth.
By sector, the "upside" surprises were broad-based, with no particular standouts, though strength was particularly notable in agriculture, manufacturing, and professional services, Stephens said.
Construction GDP contracted by 0.1 per cent compared with Westpac's expectation for a 1 per cent increase.
Statistics NZ noted that quake-related construction did not have a significant impact on the result.
The kiwi dollar gained by about half a US cent to just over US80c the back of the news.