The Bank of Scotland's latest PMI found there was "muted" demand for goods and services in March.
Business activity in the services sector dipped for the first time in four months.
However, factory production continued to rise "at a pronounced rate".
The report also noted a "fractional" rise in employment.
The PMI - which measures changes in combined manufacturing and services output - slipped to 50.1 last month, down from a 19-month high of 51.7 in February.
Any figure above 50 suggests expansion.
Firms, particularly in manufacturing, reported that unfavourable exchange rates had led to an increase in input costs. Higher wages were also reported to have pushed up operating expenses.
The survey found that companies continued to respond to higher operating costs by increasing their own charges.
Fraser Sime, regional director for Bank of Scotland Commercial Banking, said: "The economic upturn of Scotland's private sector economy lost momentum at the end of the first quarter.
"A muted demand for goods and services resulted in only a marginal increase in new business inflows, which, in turn, caused activity levels to broadly stagnate.
"The overall message is more balanced, however, as businesses created jobs over the month and sentiment remained broadly positive.
"These developments suggest that the Scottish economy will likely return to growth as we head into the second quarter."
Scotland's private sector economy stagnated last month as a downturn in services activity offset growth in manufacturing production, according to a survey of purchasing managers.