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, making him Serie A's all-time top African scorer.
Giovanni Simeone made sure the hosts would finish the season on 90 points with a stunning long-range strike before celebrating by holding up a Napoli shirt worn by icon and compatriot Maradona.
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 years old.
Napoli's title triumph was the crowning glory of Spalletti's long and eventful coaching career which had brought plenty of plaudits but few trophies.
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.
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.
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.
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".
He was then given a rousing round of applause and hugs from opposition players when he was substituted in the final moments of a procession for Napoli.
Quagliarella may continue his playing career next season as under new ownership and with bankruptcy no longer looming Samp try to return to the top flight.
Dejan Stankovic confirmed before Sunday's match that he would also leave Samp, saying to DAZN that chairman Marco Lanna told him they had to "either try to keep Sampdoria in Serie A or stop the club from going under".
Later Zlatan Ibrahimovic will say farewell to AC Milan supporters after their final game against Verona, who are fighting for their top-flight lives.
The 41-year-old was a key figure in Milan's resurgence to the top of Italian football after his return to the club as a free agent in late 2019, helping to bring them back from the doldrums and eventually win the Scudetto last season.
But he has only started one match and netted once for Milan in an injury-plagued season, a 3-1 win at Udinese in March in which he became the oldest goal scorer in Serie A history.
Swede Ibrahimovic, who is reportedly on his way to Monza next season, also won Serie A with Milan in 2011, their most recent title until last season's triumph.
Verona sit just inside the drop zone, level on 31 points with Spezia who are at Roma, and if the pair finish the season with the same tally they will contest a play-off to see who goes down to Serie B.