Messi was involved in all three goals as he beat Gianluigi Buffon for the first time in his career to open the floodgates just before half-time.
Ivan Rakitic added a second after Messi’s run and cross opened up the Juventus defence before the Argentine rounded off the scoring by drilling home his second of the evening 19 minutes from time.
Victory puts Barca on top of Group D alongside Sporting Lisbon, who were 3-2 winners at Olympiakos.
Barca’s start to the season has been dominated by calls for president Josep Maria Bartomeu to resign following Neymar’s world record move to Paris Saint-Germain and the Catalan giants’ bungled moves to replace the Brazilian.
However, Ousmane Dembele impressed on his full debut following a 105 million-euro ($126 million) move from Borussia Dortmund, as Barca proved as long as they have Messi there is life after Neymar.
Juventus showed even more upheaval since the sides last met in last season’s quarter-finals with six changes from their trip to the Camp Nou just five months ago.
The Italian champions progressed comprehensively 3-0 on aggregate back then and threatened to expose Barca again early on with Marc-Andre ter Stegen forced into three early saves to deny Mattia de Sciglio, Paulo Dybala and Miralem Pjanic.
Dembele was showing plenty of promise, but often tried to beat one man too many in his quest to impress as Barca struggled to create early on.
Their best effort before opening the scoring came when a Messi free-kick rebounded back into Luis Suarez’s path and his fierce effort was turned over by Buffon.
Dembele was involved in the move as Messi broke his personal duck against Buffon in the final minute of the first half.
Messi picked up the Frenchman’s pass before exchanging a one-two with Suarez and firing with unerring accuracy just inside the far post.
Juventus had a big chance to respond right at the start of the second half, but Dybala couldn’t match his international teammate’s finish and he lifted his shot over the bar.
Messi was inches away from his second as another rasping left-foot drive came back off the inside of the post, rebounded off the back of Buffon’s head and dropped just wide.
Yet, Messi was also fortunate to escape his first ever red card at club level moments later as he was booked by Slovenian referee Tomaz Klancnik for his attempts to get a Juventus player cautioned.
Aided by his teammates, though, Messi continued his protests and could easily have been shown a second yellow by a more stringent official.
His clash with the referee only seemed to inspire Messi to greater heights as he drove through the Juventus defence once more and, when his low cross was only partially cleared by Stefano Sturaro, Rakitic slotted home the rebound.
Buffon momentarily denied Messi his double with a fine save from a free-kick.
However, the veteran goalkeeper was helpless once more 21 minutes from time when Messi cut inside onto his left foot and buried the ball into the bottom corner for his eighth goal of the season already.