Joseph D’Amelio, 38, of East Boston, was arrested when he picked up the pills after they were delivered to an East Boston auto garage.
Police said D’Amelio pulled up to Advanced Automotive on London Street in his official marked MIT vehicle at about 6 p.m. to pick up the drugs.
Police said the package contained 340 80 milligram OxyContin tablets and 30 milligram Roxycodone tablets. Police also seized $12,000 in cash.
He was arrested along with Anthony Christallo, 39, of Derry, N.H.
Police were tipped off by security at the FedEx office who were suspicious of the package.
D’Amelio and Christallo were both charged with trafficking in more than 100 grams of OxyContin, an offense that carries a minimum of 10 years and as many as 20 years in state prison.
They will be arraigned Monday in East Boston District Court.