The 25-year-old collapsed after suffering a heart attack during the first half of the game of the match between Pescara and Livorno in Italian football's second division.
He was treated on the pitch before being rushed by ambulance to Pescara's Civile Santo Spirito hospital but was later pronounced dead.
A statement on the official Serie A web site said: "The world of soccer is in mourning for the tragedy that took place this afternoon in Pescara, where during a match between the home team and Livorno, the soccer player Piermario Morosini collapsed on the ground (struck down) by a heart attack.
"The young midfield player came under pharmacological coma, but he died around 17:00."
Morosini, a former Italy under-21 international, was on loan at Livorno from Serie A side Udinese.
The match was immediately abandoned and the Italian Football Federation (FIGC) announced a short time later that all football fixtures this weekend have been canceled.
Inter Milan captain, Javier Zanetti, who learned of the news as his team were preparing for their Serie A fixture against Udinese, said the whole team was shocked by the news.
"We're all deeply dismayed and very sorry," Zanetti said in a statement published on Inter's web site.
"It is hard to believe what has happened and of course it was right to postpone all league games. My thoughts and those of all my teammates go out to all his family," Zanetti added.
Fellow professionals have also taken to Twitter to express their sadness at the player's passing.
Manchester City's Argentine international Sergio Aguero said: "Livorno Piermario Morosini's passing is a great blow to everyone. It's a sad day for me as well. My condolences to his family."
While Wesley Sniejder of Inter Milan wrote: "Rest in peace Piermario Morosini, riposa in pace...."
Morosini's death comes just under a month after English Premier League player Fabrice Muamba collapsed after suffering a cardiac arrest during an FA Cup match between Bolton Wanderers and Tottenham Hotspur at White Hart Lane on March 17.
The 24-year-old's heart stopped for 78 minutes as doctors struggled to keep him alive at the stadium and then later at the London Chest Hospital on March 17.
The Bolton midfielder has since made a remarkable recovery.
