The Anglo-Dutch group, which is behind Dove, Marmite and Ben & Jerry's ice cream, posted a 2.6 per cent increase in underlying sales for the period to £11.8bn, below expectations and down from 3 per cent in the first half of the year.
Chief executive Paul Polman said: "Growth in the third quarter was adversely affected by poorer weather in Europe compared with last year and natural disasters in the Americas."
However, he pointed to "signs of improvement" in some of Unilever's biggest emerging markets, including India and China.
Its emerging markets division booked a 6.3 per cent increase in underlying sales over the quarter, which compares to a 2.3 per cent fall in developed markets.
However, Unilever held its underlying annual sales growth forecast at within the 3 to 5 per cent range.
Unilever, which employs 169,000 people worldwide, announced in April that it would offload some of its best-known brands - including Flora and Stork - after fending off a £115bn takeover attempt from Kraft Heinz.
It plans to sell its underperforming spreads business, which could yield up to £6bn.
Earlier this year, Unilever also struck a £1.9bn deal to buy South Korean cosmetics firm Carver Korea.
It bought the business from Bain Capital Private Equity, Goldman Sachs and the firm's founder, strengthening its foothold in the Asian beauty market.