Kiwibank has more than doubled its half year profit.
The bank, which is a subsidiary of New Zealand Post, made $37.9 million in the six months to the end of December.
That compares with $13.9 million in the same period a year earlier, when it was hit by the Christchurch earthquake and the global financial crisis.
Lending rose 5% during the period, while customer deposits rose almost 9%.
Chief executive Paul Brock says it is a strong underlying performance and customer numbers continue to grow.