Cristiano Ronaldo opened the scoring deep into first half stoppage time in Turin and then had a hand in Federico Bernardeschi netting the second after 66 minutes.
Five-time Ballon d'Or winner Ronaldo missed a late penalty but Maurizio Sarri's side moved seven points ahead of second-placed Inter Milan to seal a 36th 'Scudetto'.
The title is Sarri's first and extends a record run which Antonio Conte started with three titles from 2012 and Massimiliano Allegri continued with the following five.
Sarri's team had missed the chance to wrap up the title on Thursday when the 'Old Lady' of Italian football fell to a 2-1 defeat at Udinese.
But they made no mistake at the Allianz Stadium despite being pushed hard by Claudio Ranieri's Sampdoria, one of the most in-form teams since the return of Serie A from the three-month coronavirus lockdown.
The breakthrough game in the final move of the first half, when Pjanic cleverly rolled a pass across the penalty area to allow Ronaldo to lash home his 31st league goal of the season.
Despite losing Danilo and Paulo Dybala to injury early Juventus made sure of the title in second half when Bernardeschi pounced on the rebound of a Ronaldo shot and tapped in a decisive finish.
Sampdoria had no way back into the game and had to play the final 20 minutes a man down when Morten Thorsby was sent off for a second yellow card.