It said the proposal, which represents a premium of Unilever’s share price at the close of yesterday, "fundamentally undervalues" Unilever.
It added that it "does not see the basis for any further discussions."
Kraft Heinz's bid for the UK/Dutch FMCG giant emerged earlier today.
In a statement confirming it had made an approach for Unilever, Kraft Heinz admitted that its initial approach had been rejected, but said it "looked forward to working to reach agreement on the terms of a transaction."
But Unilever later released its own statement, making clear it would not be giving in easily.