The Bank of New Zealand-Business NZ's seasonally adjusted performance of services index (PSI) rose to 58.9, its highest since November 2007, from a revised 58.5 the previous month.
A reading above 50 indicates expansion in activity. The index involves retail trade, property and business services.
All of the PSI's five sub-indices were in expansion, with solid gains for new orders-business and activity-sales, while the employment sub-index eased slightly.
Last week, a companion manufacturing survey (PMI) showed activity slipping to its lowest level in seven months on sharp falls in production and new orders.
A composite measure of the PMI and PSI suggested the economy would grow at an annual rate of about 4 percent, the BNZ analysts said in an accompanying commentary.