The Anglo-Dutch group's revenues were 6.3% lower at 11.4 billion euros (£9.4 billion) in the first three months of the year, although it said underlying growth remained healthy with trading stronger than the rest of its markets.
When stripping out the impact of currency movements, underlying sales were 3.6% higher, with volumes up 1.9% and prices 1.6% stronger.
There was growth of 6.6% in emerging markets, but this was weaker than the annual rate of 8.4% seen in the previous three months.
Chief executive Paul Polman said: "Emerging markets are currently passing through a period of slower demand and economic volatility but our strategy remains unchanged."
Emerging markets, which account for more than half of Unilever's revenues, have been under pressure due to currency weakness in countries such as Brazil and India.
In Europe, sales were flat in the face of sluggish markets, as growth in ice cream, personal care - such as Vaseline and Dove soap - and home care offset a decline in foods due to a later Easter. The trading regions of UK and Germany boosted market share, it added.
The underlying sales growth rate was slightly ahead of City expectations but shares fell 2% due to the scale of the 8.9% negative currency impact.