Eder's long wait for an international goal came to an end as Portugal won Tuesday's friendly in Stade de Geneve 1-0 to consign Antonio Conte to his first defeat at Italy coach.
Portugal had to contend without talismanic captain Cristiano Ronaldo - who is reported to have been allowed to go on holiday rather than play in Switzerland - against Conte's side, but Eder's first goal for his country ensured they came out on top.
The Braga striker had failed to find the back of the net in 17 appearances for Portugal since making his debut back in 2012, but he converted an exquisite cross from Ricardo Quaresma - meaning Italy were beaten for the first time since losing to Uruguay in the World Cup almost a year ago.
Leonardo Bonucci hit the post just before Eder struck, as Italy were beaten four days after a 1-1 Euro 2016 qualifying draw with Croatia that left them second in Group H.
Portugal, who beat Armenia 3-2 on Saturday and are top of Group I, have now won six of their last seven matches.
Andrea Ranocchia spared Sirigu's blushes when the Italy goalkeeper looked to have gifted Portugal the lead on the half-hour mark.
Sirigu failed to deal with a backpass and Eder took advantage by intercepting before cutting the ball back for Silvestre Varela, whose placed effort was destined for the back of the net until Ranocchia intervened.
The first half was not particularly inspiring, but there was no shortage of action at the start of the second period as Bonucci met Andrea Pirlo's free-kick with an effort that came back off the post and Matteo Darmian's strike following up was deflected over the crossbar.
Portugal then moved in front seven minutes after the break, when Quaresma's sublime cross from the left with the outside of his right foot was turned in by Eder from close range.
Beto made fine saves to deny Manolo Gabbiadini and Franco Vazquez as Italy failed to conjure up an equaliser and Portugal ended the season on a high note.
