The Azzurri saw off England on Sunday on penalties after 90 minutes of normal play and a half-hour of extra-time failed to produce a winner and will now face Joachim Low's men on Thursday.
Portugal are set to play reigning champions Spain a day earlier and Mancini believes there will be some shock results in the semi-final clashes.
“The final will be between Italy and Portugal,” Mancini told Radio RAI.
The former Inter coach compared the upcoming semi-final matches to Chelsea’s surprising Champions League victory in the last four over Barcelona and Bayern Munich’s win against Real Madrid at the same stage of the competition.
“It’ll be like what happened in this season’s Champions League where favourites Barcelona and Real Madrid lost out in the last four,” he said.
Mancini made 36 appearances for his country and scored four goals, including a strike against West Germany at Euro 1988.