Guy Philippe, who led a coup that drove Jean-Bertrand Aristide from the presidency in 2004, had been due to take up his seat in the Senate on Monday, which could have afforded him immunity from some criminal proceedings.
Joris Mergelus, head of the anti-drug unit in the Caribbean nation, said Philippe was arrested by police acting on an international warrant for drug trafficking.
Philippe, who was elected senator from the southwestern Grand Anse region on Nov. 20, was picked up after giving a radio interview in Petionville, near the capital, Port-au-Prince.
Garry Desrosiers, spokesman for the Haitian national police, said that while agents from the U.S. Drug Enforcement Administration did not participate in the operation, they were at the police station where Philippe was taken.
Philippe was later put on a plane in Port-au-Prince and extradited to the United States, a Haitian official told Reuters, speaking on condition of anonymity.
Philippe was suspected in 2015 of involvement in an attack on a police headquarters in the southern city of Les Cayes in which at least six people were killed.
Haitian officials issued a warrant for Philippe's arrest over the incident, but his lawyers said it was invalid because he was a candidate in the November election.