US Marshals Service spokesman Manny Puri says Martinelli was in custody last evening at a federal detention center in Miami.
The former president was arrested earlier in the evening near his home in Coral Gables, Florida. He is accused of corruption and spying on opponents in Panama.
Martinelli is expected to appear before a judge for an extradition hearing.
The former president from 2009-2014 has denied wrongdoing and contends the case is political persecution by his successor.
In February, prosecutors in Panama also said they were seeking international help in detaining two of his sons in relation to an alleged scheme to launder bribes from Brazilian construction giant Odebrecht.