Udinese clinched a place in the play-off round of next season's Champions League qualifying tournament by winning 2-0 at Catania to finish third, leaving Lazio, Napoli and Inter Milan to contemplate the Europa League.
Antonio Di Natale, included in Italy's provisional squad for Euro 2012, opened the scoring for Udinese with his 23rd league goal of the season.
The 38-year-old Filippo Inzaghi, playing his last league game for runners-up AC Milan after 11 seasons, scored the winner in a 2-1 victory over relegated Novara.
Juventus became only the second team to win Serie A without losing a game after Fabio Capello's AC Milan in 1991/92 and the first to achieve the feat in a 38-match season.
Del Piero curled the ball in from the edge of the penalty area in the 28th minute after Luca Marrone had fired the opener for Juve who clinched the title last week.
An own goal by Stephan Lichtsteiner put a slight dampener on Juve's celebrations in the 83rd minute before defender Andrea Barzagli converted a stoppage-time penalty.
Barzagli had come on just one minute earlier following an injury to Giorgio Chiellini and became the 20th Juventus player to score a league goal this season.
"We've had a fantastic championship season, crowning it with the Scudetto and a record which will go down in history," said Juventus coach Antonio Conte. "Others can only try and equal our feat."
Club president Andrea Agnelli said last year that Del Piero's contract would not be renewed when it expires at the end of the season and seems unlikely to backtrack.
Del Piero, used sparingly by coach Antonio Conte, could still feature in one more match for Juventus when they play Napoli in the Italian Cup final on May 20.
"We all felt emotional. Alex is a great champion and will be forever remembered as an indelible part of Juve's history," added Conte. "I'm moved for him and honouring everything with the Scudetto is extraordinary."
GATTUSO'S TEARS
Milan, where midfielder Gennaro Gattuso and defender Alessandro Nesta were also playing their last home games after announcing they would leave the club, fell behind to a Santiago Garcia goal in the 20th minute.
Midfielder Mathieu Flamini equalised in the 56th minute before Inzaghi, who came on midway through the second half, grabbed the winner in the 82nd minute, firing in a half-volley from Clarence Seedorf's pass.
Tough-tackling Gattuso left the San Siro pitch in tears as he ended 13 seasons at the club.
Juventus finished with 84 points, four ahead of Milan, with the two teams taking Italy's places in the group stage of the Champions League next season.
Udinese, who had needed a draw to clinch third place, left nothing to chance with a win in Sicily.
Antonio Di Natale and Diego Fabbrini scored in each half for Udinese, who lost to Arsenal over two legs in last
