Hameed Chishti, 47, nicknamed Benny, and Wahab Chishti, 49, also known as Angel, were flown to the United States from Spain last Friday, more than a year after their arrest at American officials' request.
If convicted on all charges, they face between 25 years to life behind bars in an American prison.
They are charged with conspiring to commit narco-terrorism, to provide support to the leftist Revolutionary Armed Forces of Colombia (FARC), to import heroin into the United States and unlawfully sell missile launchers.
Prosecutors allege that the brothers agreed to sell heroin to people they believed were FARC, but who were actually undercover informants, thinking it would be smuggled into the United States.
In April 2014, the Chishtis allegedly arranged delivery of a one-kilo heroin sample to presumed FARC cronies in the Netherlands.
They then agreed to sell them weapons after the alleged FARC members claimed to want to buy Russian-made surface-to-air missiles to protect their drug-trafficking empire in Colombia.
After Hameed Chishti forwarded bank account details for payment for the missiles, the brothers were arrested in June 2014 in Spain, where they lived, prosecutors said.
They appeared before a US magistrate on Friday as prosecutors seek the extradition of two more defendants from Spain – delayed because they are seeking asylum.
The Chishtis “illustrate once again that drug trafficking and terror conspiracies often intersect, support, and facilitate each other's dangerous and potential deadly plots,” said Mark Hamlet, the Drug Enforcement Administration special agent in charge.
The United States declared FARC a terrorist organization in 1997.