Legendary player Pirlo, appointed in August following the sacking of Maurizio Sarri, saw his reign get off to an impressive start at the Allianz Stadium on Sunday.
Young midfielder Kulusevski found the net inside 13 minutes and Bonucci added a deserved second for Juve with 12 minutes to play, following up after Weston McKennie's shot was saved.
Ronaldo, who had earlier hit the crossbar, rounded out the scoring late on after being teed up by Aaron Ramsey, helping the hosts make a bright start to their latest title defence in Serie A.
Kulusevski found the net with his first shot for his new team, curling a left-footed effort away from Emil Audero after Ronaldo's run into the box was halted and the ball ran loose.
Ronaldo, who has now scored in his last four games against Sampdoria, sent a powerful strike against the underside of the crossbar as Juve pressed for a second.
Some good play from Ramsey set up Ronaldo for another opportunity before half-time, but his angled drive ended inches wide of the target.
The lively Ramsey also played in Gianluca Frabotta for a good chance early in the second half, which the surprise starter drilled on target but Audero kept out.
Juventus did eventually make their dominance tell, however, as Bonucci was first to pounce when McKennie's prodded effort was stopped after the visitors failed to deal with a corner.
McKennie was denied a debut goal by Audero's fine save late on but Ronaldo took Ramsey's pass in his stride and clinically fired home, putting the seal on a successful outing for his new head coach.
What does it mean? Pirlo already making his mark
Juve, with debutants McKennie and Kulusevski lining up in a 3-4-1-2 formation that saw youngster Frabotta at wing-back, played some stylish and exciting football.
Pirlo clearly wants his side to pass the ball around - as highlighted by having 66 per cent of the possession - and they were not afraid to shoot, firing away 20 attempts in total.
Dream debut for Kulusevski
Kulusevski was signed by Juve in a big-money deal in January but was loaned back to Parma, where his form saw him named Serie A's best young player. He picked up from where he left off last season too, netting with just his sixth touch of the ball - his one and only shot of an impressive debut – while also creating three chances.
Three goals but new striker needed
Pirlo has admitted he wants reinforcements up front, though sporting director Fabio Paratici confirmed ahead of kick-off that Luis Suarez is no longer an option. Juventus may have scored three times here, yet they struggled in front of goal between their first and second. Ronaldo finally registered with his 10th attempt of the contest.
Juventus face a potentially tricky test against Roma at the Stadio Olimpico, while Sampdoria host Benevento next weekend.