Del Piero, who after 20 years' illustrious service will leave the Turin club on the expiry of his contract this summer, slotted home Juve's second of the afternoon after Luca Marrone had opened the scoring.
Andrea Barzagli's penalty completed the victory for the hosts in stoppage time after Atalanta had been given late hope thanks to Stephan Lichtsteiner's own goal.
Juve won their 28th Scudetto last weekend when nearest challengers AC Milan lost 4-2 at Inter Milan and the Bianconeri defeated Cagliari 2-0. And the celebrations intensified today as Juve secured the result they needed to join Perugia and AC as the only clubs to have gone undefeated through an entire Serie A season.
Juventus still have one more date in their diary this term - the Coppa Italia final against Napoli in Rome next weekend - where 37-year-old Del Piero, the club's all-time record goalscorer, will have chance to make another fitting farewell to the Turin faithful.
The hosts wasted little time getting the title celebrations in full swing today as they took the lead after 10 minutes, Marco Borriello playing in Marrone who did the rest with a clinical finish high into the net.
And with 28 minutes on the clock it was two, Emanuele Giaccherini with the assist on this occasion as Del Piero picked up on the ball and lashed a low drive into the bottom-left corner from outside the box.
Giorgio Frezzolini then denied the hosts a third with a good save from Borriello on 47 minutes.
Atalanta finally threatened at the other end after 65 minutes when Giacomo Buonaventura's drive towards the top-right corner was brilliantly saved by Marco Storari.
The visitors were right back in it on 83 minutes when Lichtsteiner deflected the ball into his own net, but Juve calmed any jitters in the first minute of injury time when Thomas Manfredini fouled Borriello in the area and Barzagli tucked home the resulting penalty.