A 2-0 win over relegated Sampdoria was little more than an hors-d'oeuvre before the real reason fans jammed into the Stadio Diego Armando Maradona - to see their team lift the trophy for the first time in 33 long years.
Victor Osimhen opened the scoring from the penalty spot midway through the second half, the 26th league strike of a stunning season which made him Serie A's all-time top African scorer.
Giovanni Simeone then made sure the hosts would finish the season on 90 points in the 85th minute with a stunning long-range strike before celebrating by holding up a Napoli shirt worn by icon and compatriot Maradona.
"I don't know, the president has to decide that," Osimhen told DAZN when asked whether he might leave in a big-money summer move.
"I love the people of Napoli, they have shown me so much love. For me, I don't mind, the president decides and I will just go with the flow."
Spalletti will be on gardening leave for a year while still under contract with Napoli, and he will return to his Tuscan vineyard the oldest-ever coach to win the Scudetto at 64.
'True to myself'
Napoli's title triumph was the crowning glory of Spalletti's long and eventful coaching career which has brought plenty of plaudits but few trophies.
"I need to be true to myself, leaving was a decision I made, that I came to. Even when I'm at home it'll be like I was in the stands watching and cheering for them," said Spalletti.
Fans will be hoping that whoever takes Spalletti's place will be able to utilise the hugely talented squad assembled by outgoing sporting director Cristiano Giuntoli, as some like Osimhen are targets for richer clubs north of the Alps.
"I would tell them to trust these boys because they have a human and playing quality that means you can allow them to keep the ball rolling," said Spalletti.
Fabio Quagliarella was honoured by his fellow Napoli supporters in his final match in Italy's top-flight on an emotional day for the Samp captain.
The 40-year-old, who has scored 182 Serie A goals, openly blubbed after being given a plaque by supporters who also unfurled a banner in the stands which said "you will never be forgotten by your people", and was given a rousing applause when he was substituted late on.
Napoli fans considered him an enemy when he left for hated rivals Juventus after just one season in 2010, unaware until years later that a bizarre stalking plot had forced his departure.
Zlatan quits
Zlatan Ibrahimovic was also emotional on his AC Milan farewell, a 3-1 win over Verona which sent their opponents into a relegation play-off with Spezia who lost 2-1 at Roma.
The 41-year-old, a key figure in Milan's resurgence to the top of Italian football since his return in late 2019, was in the stands injured as he has been for most of the season ahead of a post-match ceremony in which he will say goodbye to supporters.
Ibrahimovic has only started one match and netted once for Milan this season, a 3-1 win at Udinese in March in which he became the oldest goal scorer in Serie A history.
He was hugged by Rafael Leao who after signing a new deal until 2028 with fourth-placed Milan on Friday scored twice late on to secure the win for Milan.
However, Paulo Dybala's stoppage-time penalty ensured Europa League football for Roma and sent Spezia into a one-off match next Sunday set to decide their and Verona's fate.
Roma's win means Juventus have to settle for the Conference League despite Federico Chiesa giving them a 1-0 win at Udinese, assuming they are not banned from Europe by UEFA for financial irregularities.
