Dubai Police has seized 5.7 tonnes of the amphetamine Captagon.
The operation has been hailed as one of the biggest drug busts ever recorded in the country and resulted in four arrests.
Officers were able to track two lorries carrying more than 3.5 million pills as they were driven to Sharjah.
The haul was concealed inside large drums used to transport electric cables.
“The operation was against one of the largest Captagon drug rings in the world,” said Maj Gen Abdullah Al Merri, commander of Dubai Police.
“It resulted in the arrest of four people who are part of an international drug-smuggling gang directed by a leader based in a Eurasian country.”
Officers at Dubai Police were tipped off about the illegal shipment once it arrived in the emirate from abroad.
Officials said the drugs were intended to be sent on to another Arab country after being cleared by cCustoms at Jebel Ali Port.
“A plan was set to keep the containers and the people who clear them under surveillance,” said Brig Eid Hareb, director of Dubai Police's anti-narcotics department.
He said officers kept watch on the cargo for 15 days as the suspects moved the drugs to Sharjah.
“The arrest of all four suspects was conducted in co-operation with Sharjah Police’s drug force,” Brig Hareb said.
“The gang leader was contacting one of the big drug lords abroad, trying to have the shipment sent to another Arab country.”