The Bank of New Zealand-Business NZ's seasonally adjusted performance of services index (PSI) fell to 53.1, from a downwardly revised 57.8 in January.
A reading above 50 indicates expansion in activity. The index involves retail trade, property, and business services.
Three of the PSI's five sub-indices fell, with the fall in new orders the biggest in the index's near seven-year history.
Stocks and supplier deliveries sub-indices gained, but remained in contraction.
Bank of New Zealand analysts said not too much should be read into one month's sharp movement, especially since it followed solid gains in January.
Last week, a companion manufacturing survey (PMI) showed activity was fractionally softer, but still strongly in expansion territory.
A composite measure of the PMI and PSI suggested the economy would grow at an annual rate of about 3.5 percent, the BNZ analysts said in an accompanying commentary.