Authorities arrested two suspects while they were transporting the shipment in Damascus, intended for trafficking out of the country, according to the Syrian Arab News Agency.
The Syrian Interior Ministry said that the operation is part of a broader national strategy to combat drug trafficking and enhance cross-border cooperation in addressing organized crime, according to SANA.
Early in April, Syrian and Iraqi anti-narcotics authorities seized around 1 million Captagon pills.
Since the fall of the Assad regime in Syria in December 2024, antinarcotics authorities in Syria and in Iraq have increasingly been conducting joint operations to crack down on cross-border criminal networks.
Under the former president, Bashar Assad, Syria became a hub for the production and distribution of illegal drugs such as Captagon, while the government largely ignored the concerns of neighboring countries about the negative effects this was having on the region.
Syria's Interior Ministry said on Monday that it had seized about 12 million Captagon pills as it bust a drug-smuggling network operating near Damascus.
It was one of the largest drug busts since the transitional authority seized power from former president Bashar Al Assad in December 2024.
After "precise monitoring and tracking of a smuggling network attempting to traffic large quantities of narcotics abroad", security forces seized "around 12 million Captagon pills in Al Dumayr area", AFP reported Brig Gen Khaled Eid, director of the Anti-Narcotics Department, as saying in a statement.
The leader of the network was arrested during the operation, according to Brig Gen Eid. The confiscated drugs will be destroyed.
The operation reflects the department's "determined approach to combatting smuggling, cutting off its sources and prosecuting" those involved in drug trafficking, he said.
Countries across the Middle East are working to shut down the trade in the highly addictive amphetamine, which was produced on a mass scale during Syria's civil war. Production of the drug became a key source of funding for the heavily sanctioned Assad regime.
Since Mr Al Assad's fall, the new authorities have reported major seizures of Captagon across the country. Officials in Damascus reported in June that the government had seized all Captagon production laboratories.
But neighbouring countries continue to report the interception of large shipments.
This month, Kuwait thwarted an attempt to smuggle pills with a street value of $18 million, and in September, Lebanon seized 64 million tablets in one of the largest drug busts in its history.