The former head of the CIA in Italy was sentenced to seven years in prison in absentia for the kidnapping of a radical imam in Milan in 2003 as part of the US "extraordinary rendition" programme.
Jeff Castelli was found guilty by an appeals court in Milan along with two other Central Intelligence Agency agents, who were each given six years, Italian media reported.
The three had been acquitted at their first trial because judges recognised their diplomatic immunity but prosecutors had appealed against the verdict.
Italy's top court last year upheld guilty verdicts against 23 other CIA agents over the same incident and ordered a re-trial for five Italian ex-spies accused of taking part.
Osama Mustafa Hassan, a radical Egyptian Islamist better known as Abu Omar, was snatched in the street in an operation coordinated by the CIA and the Italian military intelligence agency SISMI.
Abu Omar, who enjoyed political asylum in Italy at the time, was then allegedly taken to a US air base in northeast Italy, flown to a US base in Germany and on to Cairo, where he says he was tortured.
The "extraordinary rendition" programme was launched by then US president George W. Bush in the wake of the 2011 attacks in the United States.