Vialli, who was Mancini’s strike partner during their playing days at Sampdoria, is now part of the Azzurri’s backroom team.
The 56-year-old is working as delegation chief of the Italian national side and Mancini has praised his work at the Euros so far.
Italy – who missed the 2018 World Cup but are now on a formidable 32-match unbeaten run that includes 13 consecutive wins – have made it all the way to the semi-finals and will take on Spain at Wembley on Tuesday night for a place in Sunday’s showpiece.
“Gianluca and I have known each other for a very long time,” said Mancini on Monday.
“So it’s only natural that it’s different, I’m not necessarily saying that we grew up together, but it’s almost like that.
“We spent a number of years together, and we have relationship that goes way beyond friendship. He’s almost like a brother to me.
“But that was pretty much the case for everyone I played with in that Sampdoria side.
“There’s been an excellent rapport among everyone, between the players and the staff, and Gianluca Vialli is now getting on a bit! So we’re quite happy to listen to him when he speaks up.”