The tusks were discovered at a Dubai port in a container shipped from Mombasa, Kenya labelled as wooden furniture.
Demand for ivory in east Asia has prompted a surge in poaching in recent years, threatening the existence of animal populations.
Elephant herds in Central Africa, Kenya, Tanzania, Mozambique and South Africa have all been hit.
"It seems to have been an increasing trend over the last couple of years," said Jason Bell, head of the wildlife group's elephant programme.
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It is believed to be the biggest seizure of illegal ivory in the UAE.
"This seizure is yet another distressing indictment of East Africa, which is now recognised as a clearing house for the illegal ivory trade," said James Isiche, the fund's regional director for eastern Africa.
Most ivory was headed for Asia and particularly China, the group claimed.
"The big issue is that there seems to an increasing demand for ivory in the east and mainly China and that's what really fuels the trade at the end of the day," Bell told AFP.