Bank of New Zealand said its cash earnings came to $385 million in the first half to March, up 36 per cent compared with the same period a year earlier.
BNZ, a unit of National Australia Bank (NAB), said the result was a 17 per cent improvement on the previous six months to September, 2011.
In Australia, NAB's net profit came to A$2.05b, down 15.5 per cent compared with a year earlier.
NAB said the fall was mainly due to charges relating to the outcomes of the UK Banking strategic review and to hedging costs.
BNZ chief executive Andrew Thorburn said the bank had delivered a solid half year performance based on good revenue and deposit growth, improvements in net interest income, management of costs and a reduction in bad and doubtful debts.